v^. 



HIGH FARMING WITHOUT MANURE. 



SIX LECTURES 



ON 



AGRICULTURE, 



DELIVERED AT THE EXPERIMENTAL FARM 
AT VINCENNES. 

BY 

M. GEORGE VILLE, 

PROFESSOR OF VEGETABLE PHYSIOLOGY AT THE MUSEUM 
OF NATURAL HISTORY, PARIS. 



PUBLISHED UNDER THE DIRECTION OF 

THE MASSACHUSETTS SOCIETY FOR THE PROMOTION 

OF AGRICULTURE. 



*&s£r 



BOSTON : 

A. WILLIAMS AND CO., 

283 Washington Street. 

1879. 



Sy traaHier iiva 

WUL QU— Lite. 



3S8S 
IB73 



CONTENTS 



PAGB 

TRANSLATOR'S PREFACE 5 

LECTURE FIRST. 

(5th June, 1864.) 

On the Science of Vegetable Production 13 

LECTURE SECOND 

(12th June, 1864.) 

On the Assimilation of Carbon, Hydrogen, and 

Oxygen by Plants 27 

LECTURE THIRD. 

(19th June, 1864.) 

On the Mechanical and the Assimilable Ele- 
ments of the Soil 40 

LECTURE FOURTH. 

(2bth June, 1864.) 

On the Analysis of the Soil by Systematic Ex- 
periments in Cultivation 53 

3 



4 CONTENTS. 

LECTURE FIFTH. 

(3d July, 1864.) 

On the Sources of the Agents of Vegetable 

Productions 71 

LECTURE SIXTH. 

(10th July, 1864) 

On the Substitution of Chemical Fertilizers for 

Farm-Yard Manure 88 

APPENDIX 106 



TRANSLATOR'S PREFACE. 



The researches of M. Ville, which are now placed 
at the head of the most important discoveries Science 
has yet made for the benefit of agriculture, were, like 
all innovations, received at first with something more 
than coldness and indifference. It has ever been thus : 
the most pregnant ideas, those destined to exercise the 
happiest influences upon society, are always accepted 
with reluctance ; for they disturb preconceived notions, 
they upset so many plausible theories, and humble our 
conceit ; therefore they are always met with objections 
and opposition from your " practical men," alarmed 
at the scientific rigor of the formula, and from savants 
always disposed to oppose one theory by another. 
But true science ultimately makes its way, notwith- 
standing, by virtue of that providential power which, 
amid a host of obstacles and diversions, finally achieves 
progress. 

Many chemists, even the most illustrious, had de- 
voted themselves to the study of the natural agents of 
fertility previously to M. Ville. Their investigations 
led to most important results ; but in spite of the 
advantages they offered, they left a general impression 
of insufficiency, and discouragement soon succeeded 

5 



6 translator's preface. 

enthusiasm. Animal charcoal and guano, for exam- 
ple, gave rich harvests, but it was soon found that they 
were expedients, and not specifics. Even farm-yard 
manure justified the title of ferfect manure but very 
incompletely. It did not always respond to what was 
required of it, and moreover is not sufficiently abun- 
dant to restore to the soil all that is taken from it, as 
the residues of a harvest consumed at a distance cannot 
all be returned to the field, which, it may be said, 
leaves us with exhaustion in prospective. 

So true is this that, even where manure is collected 
with the greatest care, the necessity for supplying the 
soil with stimulants is still felt. Fossil manures pre- 
sent themselves to supply this deficiency, and they 
certainly possess great value : but do they unite every 
quality necessary to secure us against fresh disappoint- 
ment? There lies the pith of the question. 

When agriculturists demand an analysis to test the 
richness of a field and repair its losses after each har- 
vest, they lose sight of the fact that each field has its 
own peculiar wants, and what will suit one may not 
suit another. 

It is by stating the problem in these terms that M. 
Ville has arrived at its solution. He has studied the 
appetites of each plant, or at least of those three great 
families of plants upon which agricultural industry is 
mostly exercised, viz., the cereals, leguminous plants, 
and roots ; and he has deduced from this study the 
formula of a normal manure. 

There is nothing extravagant in stating that light 
has thus replaced darkness, that order has succeeded 
to chaos, and that the phantom of sterility is laid. If, 
like all mundane things, the system is perfectible, the 



translator's preface. 7 

specialization of manures — or, to speak more cor- 
rectly, the nutrition of plants — is the law which will 
make agriculture pass from the condition of a conjec- 
tural to that of a positive science. 

To operate with greater certainty, M. Ville removed 
every element of error or doubt from his experiments, 
and proceeded by the synthetic method. He took cal- 
cined sand for his soil, and common flower-pots for 
his field. Ten years of assiduous observation and ex- 
periment led him to recognize that the aliment pre- 
ferred by cereals is — nitrogen; by leguminous 
plants — potassa ; by roots — the phosphates : we say 
the preferred element, but not the exclusive: for 
these three substances, in various proportions, are 
necessary to each and all, and even lime, which humus 
renders assimilable, must be added. 

These facts, proved in pure sand by means of fer- 
tilizers chemically prepared, were next repeated in 
the soil of a field on the Imperial farm at Vincennes, 
at the expense of the Emperor, who, with that sagacity 
and tact which mark his every public act, recognized 
in M. Ville, even at the time he was violently opposed 
and unpopular, the man most capable of turning the 
conquests of science to the advantage of agriculture : 
he extended a generous and powerful hand to the Pro- 
fessor, and the most complete success has crowned his 
glorious initiative. 

During the past four years curious visitors, drawn to 
the farm by the report of M. Ville's experiments, have 
been shown a series of square plots, manured and 
sown in conformity with rules laid down to test their 
efficacy. Upon some of these plots the seed has never 
been varied ; the same soil has been planted four times 



8 translator's preface. 

in succession with wheat, colza, peas, and beet-root : 
giving them, at the commencement, a supply of the 
normal manure, and adding annually what M. Ville 
terms the dominant ingredient, that is to say, the 
special manure of the series. Upon the other plots, 
the seed alternated during the quaternary period at 
the expense of the normal manure, by changing the 
dominant according to the nature of each plant intro- 
duced into the rotation : and, under these conditions, 
the crops have reached to results of irrefutable elo- 
quence. 

But as a proof necessary to satisfy prejudiced minds, 
side by side with the plots which had received the 
complete manure, others were placed in which one or 
more of the elements were omitted. In the latter, veg- 
etation was languid, and almost nil^ proportionally to 
the quantity and quality of the absent ingredients, to 
such a degree, that what was wanting could be ascer- 
tained by the decrease of vigor in the plant. A little 
practice thus leads to an appreciation of the qualita- 
tive richness of a soil. For the suppression of one of 
the principles of fertilization produces in each vegeta- 
ble family differences, which indicate to the observer 
the part which each principle performs, and the propor- 
tion in which it is absorbed. These experiments, the 
fundamental bases of theory, have not, however, the 
regulating of agricultural practice for their object. M. 
Ville assigns four years to the action of the normal 
manure, replenished after each harvest by the domi- 
nant element ; renewing this normal manure, how- 
ever, upon the first signs of a falling off in the crops. 

By adding, according to M. Ville's system, nitro- 
genous matter, phosphate of lime, and potassa, — that 



translator's preface. 9 

is to say, a normal or complete manure to calcined 
sand, the seed-wheat being equal to i, — the crop is 
represented by 23. 

Upon withdrawing the nitrogenous matter from this 
mixture of the four elements, the crop fell to 8.83. 

Upon withdrawing the potassa, and retaining all 
the others, the crop only attained to the figure 6.57. 

When the phosphate of lime was omitted, the crop 
was reduced to 0,77 : vegetation ceased, and the plant 
died. 

Lastly, upon abstracting the lime, then the crop, 
the maximum of which was represented by 23, was 
only 21.62. 

From the above facts we draw these conclusions : 
That if the four elements of a perfect manure, above 
named, act only in the capacity of regulators of culti- 
vation, the maximum effect they can produce implies 
the presence of all four. In other words, the function 
of each element depends upon the presence of the 
other three. When a single one is suppressed, the 
mixture at once loses three-fourths of its value. 

It is to be remarked, that the suppression of the 
nitrogenous matter, which causes the yield of wheat 
to fall from 23 to 8.33, exercises only a very moderate 
influence upon the crop when the plant under culti- 
vation is leguminous. But it will be quite otherwise 
if in such case we remove the potassa. 

If we extend the experiment to other crops, and 
successively suppress from the mixture one of the four 
agents of production, we arrive at the knowledge of 
the element which is most essential to each particular 
crop, and also which is most active in comparison 
with the other two. For wheat, and the cereals gen- 



io translator's preface. 

erally, the element of fertility, far excellence, — that 
which exercises most influence in the mixture, — is 
the nitrogenous matter. For leguminous plants, the 
agent whose suppression causes most damage is po- 
tassa, which plays the principal part in the mixture. 
For turnips and other roots, the dominant element is 
phosphate of lime. 

By employing these four well-known agents, M. 
Ville's system may well replace the old system of 
cultivation. With him, the rule that manure must be 
produced upon its own domain is not absolute. Dur- 
ing four succeeding years, M. Ville has cultivated, at 
the Vincennes farm, wheat upon wheat, peas upon 
peas, and beet-root upon beet-root ; and he entertains 
no doubt that he could continue to do so for an indefi- 
nite period, the only condition necessary to be fulfilled 
being — to return to the soil, in sufficient proportion, 
the four fundamental elements above named. 

Suppose we wished to cultivate wheat indefinitely. 
We should at first have recourse to the complete ma- 
nure, and afterwards administer only the domi?iant 
element, or nitrogenous matter, until a decrease in 
the successive crops showed that this culture had ab- 
sorbed all the phosphate of lime and potassa. As 
soon as a diminution in the crops manifests itself, we 
must return to the complete manure, and proceed as 
before. 

Suppose that, instead of an exclusive culture, it be 
desired to introduce an alternate culture in a given 
field. We commence with the agent that has most 
influence on the plant with which we start. If that 
be a leguminous plant, we at first administer only 
potassa. For wheat, we should add nitrogenous mat- 



translator's PREFACE. II 

ters. If we conclude with turnips, we have recourse 
to phosphate of lime ; but when we return to the point 
from which we started, all four elements must be 
employed. 

As may be seen, this system differs radically from 
that hitherto adopted. It has not for its basis a com- 
plex manure administered to the soil by wholesale, in 
which we endeavor to turn all its constituents to ac- 
count by a succession of different crops. In M. Ville's 
system, he supplies to the soil only the four governing 
agents of production, which are added gradually, one 
after another, and in such manner as to supply each 
kind of crop with the agent that assures the maximum 
yield. 

The experiments at Vincennes were quite conclu- 
sive, but M. Ville wished to verify them on a larger 
scale. For this purpose, land on the estate of Belle 
Eau, near Donzere, in Dauphiny, was placed at his 
disposal wherein to open a new field of experiments. 
The results were just the same. On the 4th of July 
last an audience of two hundred farmers, and others 
interested in the progress of agriculture, assembled 
under the lofty trees at Belle Eau, to listen to the Pro- 
fessor's explanations, and witness the proofs of the 
soundness of his new system. 

He stated that the experimental field, divided into 
seven equal portions, was sown in November last 
with " Hallett Wheat." One portion received no 
manure at all ; consequently the product, both ears 
and straw, was weak and frail. Each of the other 
portions was fertilized with one of the substances 
which constitute wheat (phosphate of lime, potassa, 
lime, and nitrogen). They presented a series of inter- 



12 



esting products, the last of which — that is to say, the 
most advantageous as to yield — was reaped from that 
portion of the soil fertilized with an artificial mixture 
of all the constituent substances united. 

Devoid of all scientific nomenclature, which fre- 
quently embarrasses most agriculturists, M. Ville's 
lucid and brilliant expose convinced the most incred- 
ulous. Almost every auditor retired with the firm 
resolution of repeating the Professor's experiments 
himself. 

All manure must contain principles, mixed in cer- 
tain proportions, the combination of which is indis- 
pensable. In this particular M. Ville has invented 
nothing, but limited himself to the specializing and 
better defining their effects, without, however, forget- 
ting those which are purely mechanical. It remains 
now for practical men to combine and prepare fertil- 
izers of each kind, and proportion their application 
according to the rules here laid down. This is a 
simple detail of execution, and if we are compelled to 
have recourse to chemical products to complete the 
elements of fertilization, they will not replace the res- 
idues of animal consumption, nor render them useless ; 
but will allow M. Moll's beautiful formula to subsist 
in all its truth, — " The purification of cities by the 
fertilization of the country." We believe we do not 
deceive ourselves in affirming that the difficulties of 
the sewerage question will be removed from the minds 
of all, as they now are from those who have given due 
attention to the subject. 

CHARLES MARTEL. 

Ashford Cottage, Fortress Terrace, 
Kentish Town. 



LECTURE FIRST. 



ANALYSIS. 

Agriculture a Scientific Problem. — All known Plants are 
composed of fifteen Elements only, which are subdivided 
into two Groups, the Organic and the Inorganic. — Parallel 
between Vegetables and Minerals. — The Formation of the 
Vegetable due to Organic Power, which modifies the ordi- 
nary Play of Affinities. — Nature, uniform in her General 
Laws, does not pass abruptly from the Mineral to the Veg- 
etable, but through a Series of Compounds named Transi- 
tory Products of Organic Activity, which are either Hydrates 
of Carbon or Albumenoids. — These Products pass insen- 
sibly from one State to another by Chemical Reactions. — 
The Albumenoids contain Nitrogen, and present themselves 
under three essential Forms : Insoluble, Semi-soluble, and 
Soluble, to which the three Types, Fibrine, Caseine, and 
Albumen correspond. — Changes that occur during Germi- 
nation, and during the Formation of the Seed. — The greater 
Part of the Work of Vegetation may be referred to the re- 
ciprocal Action of the Hydrates of Carbon, Albumenoids, 
and Minerals, throughout which the General Laws of Chem- 
istry prevail-. — The Quantity of Mineral Matter contained 
in Vegetables is in Proportion to the Activity of Evapora- 
tion. — The Distribution of the Mineral Matter in Veg- 
etables obeys fixed Laws. — Definition. — Vegetables are 
Combinations of a Superior Order to Mineral Combina- 

13 



14 LECTURES ON AGRICULTURE. 

tions, but, like them, dependent upon the Association of the 
first Elements under the Influence of the General Laws of 
Chemistry. 



IN consequence of the persevering efforts given to 
the study of plants of late years, agricultural produc- 
tion has been raised to the rank of a scientific problem, 
tt is in this spirit that I have for many years studied 
it at the Museum of Natural History. Here, my lan- 
guage will be more simple, familiar, and practical ; 
it will, nevertheless, retain its scientific character, 
science being the essential basis of everything I have 
to tell you. 

If we seek to define the conditions which determine 
vegetable production, the influences which modify its 
growth, and the forces which govern its manifestations, 
we must commence by going back to the elements of 
vegetables themselves. We must separate from the 
vegetable its organic individuality, and consider only 
the chemical combinations of which it is the seat and 
the result. 

The analysis of all known vegetables, or the products 
extracted from them, leads to this very unexpected 
fact, — that fifteen elements only concur in these innu- 
merable formations. These fifteen elements, which 
alone serve to constitute all vegetable matter, are sub- 
divided into two groups. 

First. The organic elements, which are encoun- 
tered only in the productions of organized beings, and 
the source of which is found in the air and in water. 
They are : 

Carbon. Hydrogen. Oxygen. Nitrogen. 



LECTURES ON AGRICULTURE. 1 5 

Second. The mineral elements, which resist com- 
bustion, and which are derived from the solid crust of 
the globe. They are : 

Potassium. Sodium. Calcium. Magnesium. 

Silicum. Sulphur. Phosphorus. Chlorine. 

Iron. Manganese. Aluminium. 

Vegetables are, in fact, and from the special point 
of view where we place them, only the varied combi- 
nations of which these fifteen elements are susceptible. 
In the same way that a language expresses our most 
delicate and profound thoughts, as well as the mean- 
est, by means of the small number of letters which 
compose its alphabet, — so do vegetable productions 
assume the most varied forms and dissimilar proper- 
ties by means of these fifteen elements only, which 
compose the true alphabet of the language of nature. 

Now, if it be so, we are justified in likening the 
vegetable to a mineral combination, a more compli- 
cated one doubtless, but which we may hope to repro- 
duce in every part, by means of its elements, as we do 
with the mineral species. This proposition, how as- 
tonishing soever it may appear to you, is nevertheless 
the exact truth. To prove it to you, permit me to 
establish a parallel between vegetables and minerals, 
from the different points of view which more espe- 
cially characterize the latter. We will commence with 
their mode of formation and growth. 

First, we perceive only differences. A crystal sus- 
pended in a saline solution, grows by the deposit of 
molecules on its surface, similar in composition and 
form to those which constitute its nucleus. These 



1 6 LECTURES ON AGRICULTURE. 

molecules, diffused through the solution, obey the laws 
of molecular attraction, and thus increase the mass of 
the primitive crystal. The vegetable, on the contrary, 
does not find diffused vegetable matter in the atmos- 
phere, nor in the soil with which it is in contact. 
Through its roots and leaves it derives its first elements 
from without, causing them to penetrate into its inte- 
rior, and there mysteriously elaborates them to make 
them ultimately assume the form under which they 
present themselves to our eyes. 

We can, nevertheless, say that the process of vege- 
table production has something in common with the 
formation of a mineral. For in both cases we see a 
centre of attraction, which gathers up the molecules, 
&c, received from without. In the more simple case 
of the mineral, the combination of the elements is pre- 
viously accomplished ; only a mechanical grouping 
takes place. In the more complex case of the vegeta- 
ble, the combination and mechanical grouping are 
effected at the same time, and in the very substance of 
the plant. In both cases a formation is engendered by 
the union of definite or definable material elements. 

From the point of view of composition, vegetables 
appear at first more simple, since they are derived 
from fifteen elements only, while at least sixty concur 
in the production of minerals ; but in reality they are 
more complex, since each plant always contains the 
fifteen elements at once, while minerals, taken individ- 
ually, never contain but a very small number, five or 
six at most. Among vegetables, the combination is also 
more intimate. In minerals, each of the constituents 



LECTURES ON AGRICULTURE. 17 

preserves, up to a certain point, its individual proper- 
ties. In the sulphates, for example, it is easy to prove 
the presence of sulphuric acid by adding baryta to it, 
which gives the insoluble precipitate of sulphate of 
baryta in these salts as well as in sulphuric acid itself. 
Besides, in thus withdrawing the sulphuric acid from a 
sulphate, we have not destroyed the sulphuric acid, we 
have only displaced it. But with the group of ele- 
ments which form a vegetable it is not so ; in them, 
all individual character disappears. Who can per- 
ceive the carbon, the nitrogen, the potassa, &c, which 
constitute the plant? Only the whole manifests its 
properties, and we cannot separate an element from 
it, except by destroying it past recovery. Notwith- 
standing these essential differences, we have, never- 
theless, in both cases, to do with material combina- 
tions, that is to say, with phenomena of the same na- 
ture, one of which is more complicated than the other ; 
they are two distant terms of the same series. 

Let us conclude this parallel by comparing the 
forces which, in both cases, determine the grouping 
of the elements. When attraction is exercised at 
great distances, in the planetary spaces, for example, 
it depends only on the reacting masses, and not upon 
their nature ; when, on the contrary, attraction is 
exercised in contact, as in chemical combinations, it 
depends at the same time upon the mass and the na- 
ture of its elements. This new and more complex 
form of general attraction is called Affinity. Gravi- 
tation, the first term of the series, which we call uni- 
versal attraction, governs and harmonizes the move- 
2 



l8 LECTURES ON AGRICULTURE. 

merits of the stars ; affinity, the second term of the 
same series, regulates the play of mineral combina- 
tions. 

If we examine the formation of vegetables from this 
point of view, we shall see that it represents a still 
more complicated case of universal attraction, a third 
term of the series, if I may be allowed the expression. 
Here, in fact, the result depends at the same time on 
the re-acting masses, on the nature of the elements 
present, and on the action of a new force, situated in 
the embryo, which diffuses itself from thence through- 
out the vegetable, and impresses its special stamp upon 
the combination produced. Take two seeds of the 
same sort, having the same weight ; remove from each 
of these seeds a morsel also of the same weight, only 
let one include the embryo in the amputation, and in 
the other let the embryo be left out, and take instead a 
fragment of the peri sperm ; then put both upon a wetted 
sponge. The seed without embryo will soon enter 
into a state of putrefaction ; the other, on the contrary, 
will give birth to a vegetable capable of absorbing and 
organizing all the products resulting from the disor- 
ganization of the first. There is then in this embryo 
a new power, of organic essence, which modifies the 
ordinary course of affinities, and impresses upon the 
combinations present a special form, of which it is 
itself the prototype. 

The formation of the vegetable is not the only case 
where foreign forces come thus to modify the ordinary 
play of affinities. Mix hydrogen and nitrogen together 
in the dark, there will be no combustion. Submit the 



LECTURES ON AGRICULTURE. 1 9 

mixture to the action of the solar rays, an explosion 
immediately takes place, and the gaseous mixture is 
replaced by a new product — hydrochloric acid. Here 
then are two elements incapable of entering into com- 
bination by themselves, but which acquire this faculty 
by the intervention of a foreign force — light. Min- 
eral chemistry abounds in examples of this kind. 

In the greater complication of vegetables under 
these different relations, I consider it then to be correct 
not to see a sufficient reason for believing that nature 
has traced a line of absolute demarkation between 
minerals and vegetables, nor to admit that the laws of 
their formation have nothing in common with those 
better known laws which regulate the productions of 
the inorganic kingdom. I think, on the contrary, that 
nature is uniform in her general laws, and that by at- 
tentive observation, aided by experiment, we may 
arrive at knowing them in all their effects. I perceive, 
then, nothing irrational in the attempt to arrive at the 
artificial realization of the conditions in which they 
are exercised to produce vegetables, as science has al- 
ready succeeded in doing with minerals. This con- 
clusion will acquire, I hope, a stronger and stronger 
evidence as we penetrate deeper in our researches, 
and I shall at once give a very striking confirmation 
of it, in showing you that nature does not pass sud- 
denly from the mineral to the vegetable, from crude 
matter to organized matter, but that there exists, on 
the contrary, a class of compounds which lead us insen- 
sibly from the one to the other, and form the bridge 
which unites these two series of productions. These 



20 



LECTURES ON AGRICULTURE. 



compounds which, for this reason, we name transitory 
products of organic activity, range themselves in two 
different groups — hydrates of carbon and albumenoids. 
The following is an enumeration of them : 

TRANSITORY PRODUCTS OF ORGANIC ACTIVITY. 

Albumenoids. 



Insoluble 



Semi-Soluble 



Soluble 



Hydrates of Carbon. 

/ Cellulose, 
\ Starch, 

{Gum Tragacanth, 
Mucilages, 
Pectine, 
Gum Arabic, 
Dextrine, 
Sugars, 



Fibrine. 



Caseine. 



Albumen. 



Let us first examine the hydrates of carbon. 

Considered separately, these bodies appear very 
unlike each other. 

Cellulose, which is the prime material of all vege- 
table tissues, is hard, insoluble in water, and resists 
the action of most reagents. 

Starch presents itself in globules formed of concen- 
tric layers. It swells and forms a jelly with boiling 
water, or with a weak solution of potassa. Tincture 
of iodine turns it blue. 

Pectine also forms a jelly with water, but it exhibits 
no trace of organization, and iodine does not turn it 
blue. 

Mucilages swell in cold water, but do not dissolve. 

Gu?n Arabic dissolves in cold water. Lastly, 

Sugars dissolve and crystallize, thus presenting one 
of the essential characteristics of mineral matters. 

Thus all these bodies form a regular series, of which 



LECTURES ON AGRICULTURE. 21 

the types I have characterized are only distant terms. 
But in nature we find all the intermediates by which 
we can pass insensibly from each one to that which 
follows it. It is thus that cellulose presents itself to us 
under very different states of cohesion, from the wood 
and perisperm of the date, where it is extremely hard, 
unto the young shoots of all kinds of vegetables, and 
the skins of fruits, where it is not more solid than 
starch paste. The latter, which in the apple, potato, 
and wheat, is in solid globules, and isolated like grains 
of sand, is found in a viscid state in other plants, and 
thus passes gradually to the form of gums and muci- 
lages. Between the latter and the sugars that crystal- 
lize, we find the uncrystallizable sugars, &c. 

But the analogies which these bodies present with 
each other do not stop here. It is, in fact, possible to 
convert them artificially from one into another by the 
very simple reactions of the laboratory. Under the 
influence of dilute acids and prolonged boiling, all are 
resolved into grape sugar, which seems to be the least 
organized form, the nearest to mineral nature that the 
type can assume. As if to give a superior reason to 
all these approximations, elementary analysis assigns 
one and the same formula to all the compounds. Each 
contains twelve equivalents of carbon united to the 
elements of water, and may be thus represented : 

C i2 (HO)* 

(Carbon.) (Water.) 

which entitles them to the denomination of hydrates 
of carbon. 

Besides this series of ternary compounds, we also 



22 LECTURES ON AGRICULTURE. 

find in all vegetables the albumenoids, which, to the 
three elements above indicated, join a fourth, nitrogen, 
in an important quantity, and two others, sulphur and 
phosphorus, in very small proportions. 

These compounds, much more complex than the 
first, present themselves under three essential forms : 
insoluble, semi-soluble, and soluble, to which the 
three types, fibrine, caseine, and albumen respond. 
Like the preceding, they are met with in nature under 
very varied conditions, and may be converted, one 
into another, by the reactions of the laboratory. 

The hydrates of carbon and the albumenoids form, 
then, two parallel series, which exist side by side in 
the substance of all vegetables, and which are con- 
stantly undergoing the various transformations of 
which they are susceptible. 

Let us show what takes place during the germina- 
tion of a grain of wheat. The hydrate of carbon 
exists in the dried grain under the form of starch, and 
the albumenoid under the form of fibrine or gluten. 
In proportion as the water penetrates the peri sperm, 
it swells, becomes milky, and then it contains albu- 
men, and dextrine, and true gum. Subsequently, when 
the blade is elongated, when the leaf begins to respire, 
you will find sugar and cellulose, which are produced 
at the expense of the original starch. By the side of 
these bodies you will find albumen derived from the 
gluten. 

Let us examine, on the other hand, what takes place 
during the formation of the seed. In beet-root, for 
example, sugar exists. In proportion as the seed is 



LECTURES ON AGRICULTURE. 23 

formed the sugar disappears, but on the other hand, 
the seed is full of starch. During the foliaceous life 
of the plant, its juice contains albumen ; when the seed 
is formed, the greater portion of the albumenized prin- 
ciple is found concentrated in an insoluble form. 

We are then fully justified in believing that these 
bodies are being constantly transformed into each other 
in the very substance of the vegetable, and that they 
are like the several steps of a ladder, by which crude 
matter gradually ascends to the rank of completely 
organized matter. 

But we have seen that in the laboratory these trans- 
formations are effected by energetic chemical agents. 
What can be the cause which determines these same 
effects in the substance of the plant ? 

When sulphuric acid converts baryta into the sul- 
phate of that base, it combines with it, and there no 
longer exists either baryta or sulphuric acid. The two 
constituents are confounded in the product of the 
combination, which is sulphate of baryta. 

When the same acid converts starch or cellulose 
into sugar, things do not proceed exactly in the same 
manner. After the transformation, we find the acid 
wholly free. By its presence alone it acts like the 
solar ray upon the mixture of chlorine and hydrogen : 
and sulphuric acid is not the only body which pos- 
sesses this property. The albumenoids, of which we 
have just spoken, possess it in a higher degree, espe- 
cially when they have begun to undergo a change by 
contact with the oxygen of the atmosphere. 

Putrid gluten rapidly converts considerable quanti- 



24 LECTURES ON AGRICULTURE. 

ties of starch into dextrine and sugar, and that without 
being itself disturbed by the exercise of its own modi- 
fications. The cause of the changes which the hy- 
drates of carbon undergo in the substance of vegeta- 
bles resides therefore in their encounter with the 
albumenoids, which are themselves modified under 
the influence of water, the oxygen of the atmosphere, 
and the mineral agents derived from the soil. 

We may then, finally, refer the greater part of the 
work of vegetation to the reciprocal action of the hy- 
drates of carbon, albumenoids and minerals. 

You perceive that all through this extremely com- 
plicated chemical operation, we always encounter the 
application of the general laws of chemistry, for the 
actions of contact are not peculiar to vegetables. They 
are also frequently encountered in the reactions which 
are effected without organic agency, only they pre- 
dominate in the phenomena of vegetable life. 

The study to which we devote ourselves, therefore, 
warrants the parallel we have drawn between minerals 
and plants, from the point of view of the superior laws 
of their production. I shall conclude by confirming 
this resemblance, and showing you that the separation 
in the substance of the vegetable of the various ele- 
ments composing it, is submitted to a law as well 
determined, I may say, almost as geometrical, as the 
arrangement of the molecules in a crystallization. 

Let us begin with the minerals. Considered as a 
whole, they are more abundant in grasses than in trees. 
The latter contain only I per ioo upon an average, 
while grasses contain from 7 to 8 per 100. 



LECTURES ON AGRICULTURE. 25 

The reason of this is very simple. In a salt marsh, 
the quantity of salt deposited in summer is more con- 
siderable than that produced in winter, because during 
summer the temperature being higher, the evapora- 
tion is more active. So also in vegetables, the quan- 
tity of mineral matter they contain is great in propor- 
tion to their evaporation. Now herbage being in 
contact with the atmosphere in every part, it is the 
seat of an evaporation much more active than that in 
trees, which contain completely sheltered organs. We 
find a rigorous application of this law in the tree. The 
sapvvood contains less mineral matter than the heart, 
the heart less than the bark, the bark less than the 
leaves. In the green leaves of trees there is less than 
in the leaves that fall in autumn. 

In leguminous plants, the pod is richer than the 
seed, and in the seed there is more in the skin than in 
the bean. The distribution of mineral matter in the 
substance of a vegetable obeys, therefore, an invariable 
law : it is in' direct relation with the activity of evapo- 
ration. If we examine what takes place with regard 
to the nature of the elements, we see that here also 
fixed laws prevail. Phosphoric acid, potassa, and 
magnesia prevail in the seeds, the alkaline earths and 
iron, on the contrary, prevail in the stalks. 

The alkalies increase in proportion as we approach 
the fruit and young shoots. They are much less abun- 
dant in those organs which are old and have less vital 
activity. 

Phosphoric acid is disseminated in a nearly uniform 



26 LECTURES ON AGRICULTURE. 

manner throughout the vegetable, and suddenly in- 
creases when it arrives at seeding. 

As to the organic elements, the laws are no less pre- 
cise. Carbon, oxygen, and hydrogen, which, in the 
state of hydrates of carbon, form the general frame- 
work, are found diffused nearly uniformly throughout 
all the organs. Nitrogen, which forms an essential 
portion of the albumenoids, of which the most impor- 
tant part consists in the active task of the formation of 
the tissues, is found in the greatest quantity in all the 
recent shoots, and especially in the seed, the last prod- 
uct of annual vegetable activity. 

We have arrived in this lecture at defining vegeta- 
bles as material combinations of an order superior to 
mineral combinations, but, like them, dependent upon 
the association of the first elements under the influence 
of the general laws of chemistry. This definition leads 
us invincibly to the hope of producing them artificially, 
and in every part, by means of their elements placed 
at our disposal, under conditions where tbey are sus- 
ceptible of assuming this kind of combination. It 
remains for us to examine the means we can employ 
to attain this aim. 



2 9 



LECTURE SECOND. 



ANALYSIS. 

The Organic Elements of Vegetables are Oxygen, Hydrogen, 
Carbon, and Nitrogen. — Under what Influences and Con- 
ditions these Elements enter the Vegetable from without. 

— Carbon enters the Plant under the Form of Carbonic Acid, 
which is absorbed by the Roots, and by green Leaves under 
the Influence of Solar Light, and emitted from the Leaves dur- 
ing Darkness. — Oxygen is disengaged from the Leaves in 
exact proportion to the Quantity of Carbonic Acid absorbed. 

— What becomes of the Carbonic Acid absorbed? — It is 
decomposed, its Carbon fixes itself in the Vegetable while 
its Oxygen is removed. — Unlimited Supply of Carbonic Acid 
from the Respiration of Animals, from the Formation of 
Pyrites, and from Volcanoes. — Carbon forms about fifty 
per cent, of dried Plants. — The Quantity fixed depends 
upon the Extent of their Foliage. — Water the Source of 
the Oxygen and Hydrogen in Plants : is sometimes de- 
composed, like Carbonic Acid, that its Oxygen may be 
eliminated. — Plants contain only small Quantities of Ni- 
trogen, but it is an indispensable Element. — They contain 
much more Nitrogen than is supplied by Manure; which 
Excess is obtained from the Atmosphere. — The Nitrates 
occupy the first rank among the Nitrogenous Matters useful 
to Vegetation. — Next come Ammoniacal Salts. — Some 

27 



26 LECTURES ON AGRICULTURE. 

' Crops do not require the Addition of Nitrogen to the Soil. 
— The Cereals require this Addition in large Quantities. 



IN our first discourse we arrived at the consideration 
of the vegetable as a material aggregate, having the 
closest analogy with chemical combinations. We have 
seen that the laws which preside at its formation differ 
in no respect, in a philosophical point of view, from 
those which regulate the production of the compounds 
of mineral chemistry. 

If it be so, in order to penetrate the mysteries of the 
production of vegetables, the first thing we have to do 
is to ascend to the origin of their elements, and after- 
wards inquire in what conditions, and under what in- 
fluences, these elements enter from without, and com- 
bine together in a special manner to produce the 
vegetable. 

Let us commence this study with the organic ele- 
ments, which are : 

Carbon. Hydrogen. Oxygen. Nitrogen. 

The carbon cannot penetrate vegetables, except under 
the form of carbonic acid. This gas arrives by two 
different wa\'s. 

ist. By the roots, which draw it from the soil, 
where it is produced by the spontaneous decomposi- 
tion of organic matters. 

2d. By the leaves, which take it from the atmos- 
pheric air, where it exists permanently. 

In order for the carbonic acid to be absorbed, it is 
necessary that four essential conditions be realized. 



LECTURES ON AGRICULTURE. 2Q. 

The first is of organic nature, and resides in the 
green color of the organs of vegetables. The petals 
of flowers which are variously colored do not absorb 
carbonic acid : the leaves, the bark, and the pericarp 
of green fruits, on the contrary, absorb it in abundance. 
In the generalization of this fact it may be objected 
that purple leaves, and leaves that are almost white, 
exist, which also absorb carbonic acid from the air. 
I find the reply in a recent work by M. Cloez. This 
chemist has shown that the leaves referred to, not- 
withstanding their different aspect, contain large quan- 
tities of green matter. It is, then, safe to say that the 
function under consideration depends upon this green 
matter. 

Whatever the color of the organs, carbonic acid is 
never absorbed in the absence of solar light. This 
second external condition of the vegetable is also as 
indispensable as the first. Would you wish to prove 
it? Pass a current of air into a large receiver contain- 
ing a young vine with its leaves, and connected with 
an apparatus capable of measuring carbonic acid. You 
will perceive, as M. Boussingault has done, that in the 
sun, the atmospheric air, in passing over the green 
leaves, loses nearly one-half its carbonic acid, while in 
the dark, on the contrary, it gains a very considerable 
quantity. Not only, then, the leaves absorb no car- 
bonic acid in the dark, but they also constantly emit 
it, to the destruction of a portion of their substance. 
When the leaves are attached to the plant, they disen- 
gage more carbonic acid than when they are removed, 
because that which the roots derive from the soil, not 
being decomposed in the vegetable, comes then to be 
exhaled from the surface of the leaves. 



30 LECTURES ON AGRICULTURE. 

A third indispensable condition, also, is the inter- 
vention of a certain temperature. MM. Gratiolet and 
Cloez have shown that the leaves of the fotamogeton, 
which, in water at 54 F., disengages abundance of 
oxygen, ceases to do so when the temperature is 
lowered to 37 F. Now, as we shall soon see, this 
disengagement of oxygen is precisely the certain index 
of the absorption of carbonic acid. 

Finally, the fourth and last condition of the phe- 
nomenon is the presence of oxygen in the atmosphere 
in which the leaves are placed. Theodore de Saus- 
sure has proved that in an atmosphere of hydrogen or 
nitrogen, containing carbonic acid, this gas is not ab- 
sorbed by plants. On the contrary, the phenomenon 
manifests itself whenever oxygen forms a portion of 
the surrounding gases. 

What becomes of the carbonic acid thus absorbed 
by plants? While this substance resists the highest 
temperatures and the most powerful chemical reducing 
agents, in the substance of plants this acid is decom- 
posed, its carbon fixes itself in the vegetable, and its 
oxygen is removed. Hence the disengagement of 
oxygen which takes place on the surface of leaves 
immersed in water. This fact, one of the most impor- 
tant which science has discovered in this century, has 
been brought to light by the labors of a whole genera- 
tion of savants, but it was principally by Theodore de 
Saussure that the conditions were defined. He saw 
that the quantity of oxygen emitted was equal in vol- 
ume to the carbonic acid absorbed, and that minute 
quantities of nitrogen were disengaged. This disen- 



LECTURES ON AGRICULTURE. 3 1 

gagement of nitrogen, since proved by MM. Gratiolet 
and Cloez, has recently been denied by M. Boussin- 
gault. 

Not wishing to insist upon this point, which has 
no interest in agriculture, I shall merely remark that, 
in all the experiments made, one condition,which could 
alone give value to their results, has been wanting. 
For it to be legitimate, in fact, to extend to vegetation 
the facts observed in these experiments, they must be 
performed upon vegetables in process of development, 
constantly increasing in weight, and not upon detached 
portions, which may, it is true, still give vital manifes- 
tations, but the ephemeral existence of which is neces- 
sarily accompanied by special phenomena of destruc- 
tion. 

The assimilation of the carbon, so interesting in a 
physiological point of view, presents only an insignifi- 
cant interest for agriculture : there need be no fear of 
its ever failing, for the atmosphere contains an unlim- 
ited supply of it. In proportion as vegetation appro- 
priates it, animal respiration, by an inverse effect, 
restores it in equivalent quantities. This harmony 
between the two organic kingdoms, first observed by 
Priestley, and so brilliantly explained by Dumas in his 
Statistics of Organized Beings, is nevertheless only 
an infinitely small one among the causes of the per- 
manence of the atmospheric carbonic acid. 

Among geological phenomena, causes of loss exist 
which are much more powerful than vegetable absorp- 
tion. The disintegration of felspars removes colossal 
quantities of this acid from the air ; but volcanoes and 



32 LECTURES ON AGRICULTURE. 

the formation of pyrites constantly restore it in quanti- 
ties no less important, so that its composition presents, 
under this relation, quite a satisfactory stability for 
agriculture. 

Carbon enters into the composition of all plants in 
the proportion of about 50 per 100, when they are 
dried. It is to this element that the variation in the 
weight of crops is due. The quantity plants assimilate 
depends, in great measure, upon the surface of their 
leaves, and also a little upon their special nature. 
Experiment has proved that plants which, upon an 
equal surface of ground, fixed most carbon, were those 
that presented the greatest foliaceous surface. We 
have seen, also, that with an equal surface of leaves 
plants fix quantities of carbon differing a little accord- 
ing to the species. 

The oxygen and hydrogen found in vegetables are 
undoubtedly derived from water; this latter may be 
assimilated naturally, as is proved by the existence of 
hydrates of carbon in the substance of vegetables in 
which oxygen and hydrogen are found in the propor- 
tions necessary to form water. But the formation of 
resins, essential oils, and fat bodies, in which hydro- 
gen predominates, shows that, in certain cases, water 
may be reduced, like carbonic acid, and that its oxygen 
may be eliminated. Whatever it be, the origin of the 
oxygen and hydrogen once established, we have no 
need to dwell on this point, for the plants, not being 
deficient of water, are in consequence abundantly pro- 
vided with these two elements. 

It is not the same with nitrogen. Plants contain it 



LECTURES ON AGRICULTURE. ^3 

only in relatively very small quantities, but they have 
an indispensable need of it, and as in certain cases it 
may fail, it is necessary to study with the greatest care 
everything that concerns the assimilation of this ele- 
ment. 

First let us show that all plants exhibit in the crops 
a much greater proportion of nitrogen than there was 
in the manure supplied to them. The following data, 
taken from Boussingault's " Rural Economy," estab- 
lish this fact. 

Annual Excess of 
Plants. Nitrogen per Acre. 

( Potatoes, "I 
Rotations of Wheat, ^ 

Five Years, plover, 

1 lurnips, 



Oats, 
r Beech, 

Forest culture, gg]^ \ 29-04 
I Poplar, J 

Exclusive culture, Artichokes, 37*S4 

Exclusive culture, Lucern, 182-06 

If the crops contain such quantities of nitrogen of 
which the soil can render no account, we must look 
to the atmosphere as its origin. The air contains 79 
per 100 of elementary nitrogen : nothing appears more 
rational than to find there the origin sought. But 
chemists, accustomed to see nitrogen gas offer a great 
resistance to combination, have at first preferred to re- 
fuse to it all intervention in the phenomena of vegeta- 
tion. To restore it to the place which this precon- 
ceived opinion, or one founded upon incomplete 
experiments, had caused it to lose, it was necessary to 

3 



34 LECTURES ON AGRICULTURE. 

have recourse to extremely delicate experiments, which 
it is impossible to describe in this place. 

I shall, therefore, content myself with refuting, by 
arguments derived from extensive cultivation, all the 
origins which the adversaries of the absorption of 
gaseous nitrogen are compelled to put forth, referring 
to my works and to my lectures at the Museum those 
among you who desire to know the direct proofs of 
this absorption. 

Priestley and Ingenhouz believed in the assimilation 
of the elementary nitrogen of the atmosphere. Theo- 
dore de Saussure having proved the existence of am- 
monia in the air, attributed to this compound the 
faculty of supplying nitrogen to vegetables. Am- 
monia does in fact exist in the atmosphere, but the 
quantity is so small (22 grammes in 1 million kilo- 
grammes), that it is evidently absurd to endeavor to 
make it play so important a part. 

The objection has also taken another form. It is 
urged that the air contains ammonia. Rain water dis- 
solves it, condenses it, and conveys it to the plant, 
which thus finds it in the soil. If in the place of thus 
contenting themselves with this vague assertion, they 
had thought to give it precision by measuring the am- 
monia in the rain water, and ascertaining the quantity 
of this water received per acre, they would have found 
by this way, that the soil receives, as a maximum, 
about 3 pounds of nitrogen per annum. But to ex- 
plain the vegetation of lucern we must account for 
1S2 pounds of nitrogen. The ammonia in rain water 
is then only infinitely small in relation to the phenom- 
enon under consideration. 



LECTURES ON AGRICULTURE. 35 

Ammonia failing, recourse was had to nitric acid, 
which is formed in the atmosphere by the direct com- 
bination of oxygen and nitrogen under the influence of 
electric discharges and during rain storms. And anal- 
ogous calculations to the preceding show that, by this 
new way also, i acre of land receives 3 pounds of ni- 
trogen, at the most. Nitric acid, therefore, explains 
no better than ammonia the excess of nitrogen in the 
crops. 

But, it is urged, there may exist in the atmosphere 
some nitrogenous substance eminently assimilable, 
which is condensed by rain water, and which has hith- 
erto escaped analysis. Notwithstanding the utter 
vagueness of this objection, I have wished to reply to 
it by direct experiment. I have instituted two similar 
growths in boxes placed under shelter ; one of them 
was watered with rain water collected by a pluviome- 
ter of equal surface to that of the box, and placed 
apart; the other received similar quantities of perfect- 
ly pure distilled water. The crop with distilled water 
was nearly as large as that obtained with rain water. 
It is, therefore, evident that rain water contained noth- 
ing susceptible of influencing the development of veg- 
etables. 

But, since it has been desired to give this importance 
to the essential products the air may yield to the soil, 
it will be permitted to me, on the other hand, to con- 
sider those which the soil yields to the atmosphere ; 
and this time it is from my adversaries themselves that 
I borrow the bases of my arguments. 

M. Boussingault had the idea of collecting the snow 



36 LECTURES ON AGRICULTURE. 

from the surface of the ground and the terrace of a 
garden. A litre of water from the first contained 
0*0017 gr. of nitrogen, while that from the terrace 
contained 0*0103 gr. It is certain, therefore, that cul- 
tivated soil constantly loses nitrogen. If we suppose 
that the layer of snow examined by M. Boussingault 
had a thickness of only o*oi m., it contained in 1 acre 
1S0 pounds of nitrogen lost to the soil. We see, then, 
that the losses the soil is capable of experiencing are 
quite as important as the gains it may derive from the 
atmosphere. We must necessarily, then, have recourse 
to elementary nitrogen to explain the excess in the 
crops. 

But here another subject of discussion presents 
itself; the nitrogen of the air — is it absorbed natu- 
rally by plants, as I have always maintained, or does 
it take place, as recently suggested, only by the inter- 
medium of nitrification previously accomplished in the 
soil, which would thus be a real artificial nitre-bed? 
Doubtless, in certain cases, important quantities of 
nitrates may be produced in the soil ; but I none the 
less persist in saying that nitrification cannot account 
for the excess of nitrogen in the crops. For the 182 
pounds to have penetrated into the lucern by this 
channel, it would have been necessary to engage 1756 
pounds of nitric acid, which itself, to be saturated, 
must have combined with 1540 pounds of bases. 
These 1540 pounds of bases should be found in the 
crops ; but the latter produced, upon combustion, 
only 1525 pounds of ashes, of which the bases formed 
701 pounds. There is, then, at least half the excess 
that the hypothesis of a nitrification cannot explain. 



LECTURES ON AGRICULTURE. 37 

Besides, if it were so, if the nitrogen of the crops 
came from the nitrogen formed in the soil, is it not 
evident that an artificial addition of nitrates would 
produce the same effect as a natural formation ? 

Now there exist, in fact, some crops, that of wheat, 
for example, the addition of nitrates to which increases 
the yield. But there are others, as you may see for 
yourselves by inspecting the experimental field, upon 
which nitrates exercise no influence. Peas, for exam- 
ple, have not assimilated more nitrogen with a strong 
manure of nitrates than without the addition of any 
nitrogenous compound. It is then quite evident that 
if, in certain cases, natural nitrification can play a defi- 
nite part, it may, on the other hand, serve as a general 
explanation of the excess of nitrogen in the crops, and 
that the true and great origin of this nitrogen resides 
in the atmospheric nitrogen directly absorbed. 

And moreover, what is there, in a theoretical point 
of view, so repugnant to the admission of this absorp- 
tion? As we speak of nitrification in the soil, who 
can deny that in the substance of leaves, where nitro- 
gen undoubtedly penetrates, where it constantly meets 
with nascent oxygen, ozonized — the formation of 
nitric acid must be at least as easy as it is in the soil? 
And when we perceive these organs endowed with a 
chemical power sufficient to reduce carbonic acid, is it 
then inconceivable that they are capable of causing 
nitrogen to enter into combination more readily than 
it does in our laboratories? No! the absorption of 
nitrogen, proved by experiment, is not irrational, and 
it is only habit and prejudices that oppose this doctrine, 



38 LECTURES ON AGRICULTURE. 

which, alone, is susceptible of giving us the clue to 
the phenomena of vegetation, and reacting usefully 
upon agricultural practice. 

If the nitrogen of the air can contribute to vegeta- 
ble nutrition, is it to be said that we are not to trouble 
ourselves about supplying nitrogen to our crops, and 
that with regard to this element we find ourselves in 
the same state of security and weakness as with the 
first three that occupied our attention? Doubtless no ! 
Practice on a large scale has proved the utility of 
nitrogenous manures, and I have myself proved that 
the yield of the cereals is considerably increased by the 
introduction of nitrogenous material into the soil. 

Of all the substances I have tried, the nitrates have 
always given me the best results, when I have oper- 
ated on a small scale, and when the quantity of nitrogen 
supplied to the crops was inferior to that which the 
yield should have contained. On the large scale, M. 
Kuhlmann has obtained similar results. But at the 
experimental farm, at Vincennes, I have observed no 
difference between the employment of nitrates and of 
ammoniacal salts. This is due, doubtless, to the ma- 
nures I had recourse to, and which I intended for sev- 
eral successive years, having been supplied in very 
large quantities, and that the plants, always finding in 
the soil an excess of assimilable nitrogen, prospered 
as well in one case as in the other. 

Therefore I do not hesitate to say that I place the 
nitrates in the first rank among nitrogenous matters 
useful to vegetation. Next come ammoniacal salts, 
and, a long way after them, organic nitrogenous mat- 



LECTURES ON AGRICULTURE. 39 

ters, which, to act usefully, must be previously con- 
verted into nitrates or ammoniacal salts. 

All that we have said concerning nitrogen may be 
summed up in the following conclusions, the agricul- 
tural importance of which cannot be questioned. 

1. Generally speaking, the nitrogen of the air enters 
into the nutrition of plants. 

2. In connection with certain crops, especially veg- 
etables, this intervention is sufficient, and the agricul- 
turist has no occasion to introduce nitrogen into the 
soil. 

3. With regard to the cereals, and particularly dur- 
ing their early growth, atmospheric nitrogen is insuffi- 
cient, and to obtain abundant crops it is necessary to 
add nitrogenous matters to the soil. Those which 
best fulfil this object are the nitrates and ammoniacal 
salts. 



LECTURE THIRD. 



ANALYSIS. 

On the Assimilation of Mineral Elements which penetrate 
the Plant in Aqueous Solution only. — The Medium from 
whence the Roots obtain them. — The Soil is the Support of 
the Roots, the Recipient of the Solution that feeds them, 
and the Laboratory where this Solution is prepared : it is 
composed essentiallj- of three Constituents : Humus, Clay, 
and Sand. — Properties of Humus : its Influence in the Soil 
fixes the Ammonia, is a constant Source of Carbonic Acid 
which dissolves the Mineral Matters, and is the principal 
Agent in supplying Plants with their Mineral Constituents. 
— Utility of Clay in Arable Land : imparts Consistence to 
the Soil, retards the Passage of Water, fixes Ammonia, 
and removes a large Quantity of Salts from Saline Solu- 
tions, storing them up for future Supply; establishes an 
Equilibrium between Seasons of Drought and Rainy Wea- 
ther. — Sand forms part of every Soil ; forms its principal 
Constituent, communicating to it its principal Physical 
Properties, especially its Permeability to Air and Rain Wa- 
ter; it tempers the Properties of Clay. — Elements of the 
Soil, without which Vegetable Life is impossible : Phos- 
phate of Lime, Potassa and Lime, which associated with a 
Nitrogenous Substance, and added to any kind of Soil, 
suffice to render it fertile. — Chemical Analysis fails when 
applied to Soils. — Necessity for substituting an artificial 

40 



LECTURES ON AGRICULTURE. 



4 1 



known Compound in Experiment, to remove all Source of 
Error. — Results obtained: i. With calcined Sand alone. 
2. With Calcined Sand and Nitrogenous Substances. 3. 
With Calcined Sand and Mineral Substances. — Each Agent 
of Vegetable Production exercises a double Function. 1. An 
Individual Function, variable according to its Nature. 
2. A Function of Union. — Special Action of Nitrogenous 
Matter and Mineral Substances. — Results. — A Soil capa- 
ble of producing Plants must contain, in an assimilable 
Form, Nitrogenous Matter, Phosphate of Lime, Potassa, 
and Lime. — Errors committed in applying Manure to Soils 
the Composition of which is unknown. — The Source of 
Error removed by the Experiments now described. — Pros- 
pect opened by Science to Agriculture. 



I^HE logical order of our inquiries conducts us 
immediately after the assimilation of the organic 
elements treated of in our last lecture, to the same 
question in respect to the mineral elements. But 
these bodies penetrate the vegetable only under the 
form of aqueous solution ; and before showing you 
the effects they produce, when absorbed, it is neces- 
sary that I should make known to you the medium 
from whence the roots derive them. 

The soil is, at the same time, the support of the 
roots, the recipient of the solution that feeds them, 
and the laboratory where this solution is prepared. It 
is composed essentially of three constituents, which 
concur, each in a certain proportion, to give to the 
whole the properties which I proceed to enumerate. 
They are Humus, Clay, and Sand. 

Humus is of organic origin. It possesses a deep 



42 LECTURES ON AGRICULTURE. 

brown color, almost black. It is the cause of the dark 
color of vegetable mould. It dissolves in alkalies, with 
which it produces an almost black liquor. Acids sep- 
arate it from this solution under the form of a light, 
flocculent precipitate of a deep brown color. While 
it remains moist it will dissolve slightly in water, but 
when once it is dried it will no longer dissolve in it. 
It does not crystallize ; and under the action of heat 
it is decomposed, leaving a carbonaceous residue. 

Such are the properties which chemists assign to 
humus, but there is nothing very characteristic, noth- 
ing to show that humus is of a very definite chemical 
species. In fact; chemistry experiences the greatest 
difficulties whenever it attempts to specify a body 
which does not crystallize, and which is not volatile. 
For in that case we can proceed only by way of 
induction. This is what we shall attempt to do in 
order to arrive at a clear idea of the constitution of 
humus. 

If we submit to the controlled action of heat the 
hydrates of carbon described in our first lecture, sugar 
for example, it will not be long before we produce a 
brown body which is designated by the name of cara- 
mel. The chemical composition of this caramel is 
nearly the same as that of the sugar from whence it is 
derived, showing that the only difference existing be- 
tween them consists in the loss experienced by the 
sugar of a certain quantity of water. Sugar being 
represented by the formula C 12 H 12 O 12 or C 12 (HO) 12 ; 
caramel is expressed by C 12 (HO) 9 . When we act 
upon sugar with hot baryta water, we obtain another 



LECTURES ON AGRICULTURE. 43 

brown body, apoglucic acid or assamare, containing 
still less water than caramel. By the action of an 
excess of alkali upon sugar we descend to melassic 
acid, which always contains hydrogen and oxygen in 
the proportions necessary to form water, but in still 
less quantity than the preceding bodies. 

It is then possible, by the reactions of the labora- 
tory, to remove successively from the hydrates of 
carbon, and, as it were, molecule by molecule, the 
greater part of the water that enters into their compo- 
sition, without their departing in consequence, from 
the original type, as in these various products the 
carbon always remains associated with the elements 
of water, and all may be represented by the general 
formula of hydrates of carbon C 12 (HO) n . 

Now this gradual decomposition of the hydrates of 
carbon goes on incessantly in arable land, where veg- 
etable debris of all kinds is buried. 

Humus is nothing more than the ordinary limit of 
this decomposition. Some chemists assign to it the 
formula C 12 H 9 O 9 ; but it is rather a collection of 
every kind through which the progressive decomposi- 
tion of the hydrates of carbon passes, and I have no 
doubt that we can go much beyond the formula ex- 
pressed by C 24 (HO) 9 . Coal, studied from this point 
of view, furnishes us with valuable instruction. 

Death thus realizes a series of phenomena exactly 
the reverse of those produced in the substance of 
living vegetables. For, while among these latter the 
carbon, reduced from carbonic acid, fixes upon the 
elements of water in greater or lesser proportion to 



44 LECTURES ON AGRICULTURE. 

produce all the hydrates of carbon, — in the soil, on 
the contrary, the water separates little by little from 
the carbon to arrive finally at leaving it almost in a 
state of liberty. 

If the chemical properties of humus are difficult to 
characterize, its presence in the soil is none the less 
useful to agriculture. It absorbs water with great 
energy, and greatly increases in volume under its in- 
fluence. By this property it contributes to maintain 
the coolness of the soil by retarding its drying. 

When humus is put in contact with an ammoniacal 
solution, it removes the ammonia from it, but retains 
it only by a very feeble affinity, for it is only necessary 
to introduce a large quantity of water to recover it. 
However, it does not fix combined ammonia ; that is to 
say, when it is combined in ammoniacal salts. Mixed 
with carbonate of lime or marl, does it acquire the 
faculty of fixing ammoniacal salts also? 

By this manner of comporting itself with ammonia 
and ammoniacal salts, the utility of which is recog- 
nized in our previous lecture, humus renders impor- 
tant services to vegetation. It prevents, at least par- 
tially, the loss of ammonia, which results from the 
spontaneous decomposition of nitrogenous organic 
matters buried in the soil. 

Moist humus, exposed to the air, undergoes a slow 
combustion, which makes of it a constant source of 
carbonic acid. The part played by this acid in vege- 
table nutrition is of the highest importance, as was 
shown in the preceding lecture : still the small quan- 
tity produced by the decomposition of humus can 
scarcely, by its direct absorption, favor the develop- 



LECTURES ON AGRICULTURE. 45 

merit of plants which otherwise find it abundantly in 
the atmosphere. Besides, we do not attach very great 
importance to the humus under this relation. But the 
carbonic acid which it unceasingly produces in the 
soil fulfils another function, incomparably more use- 
ful. It serves to dissolve the mineral matters, phos- 
phates, alkalies, lime, magnesia, iron, etc. It causes 
the disaggregation of fragments of rocks containing 
useful matters which water alone cannot attack, and 
which, without it, would remain inert in the soil. 
Carbonic acid derived from humus is then, as a whole, 
the principal agent of solution capable of supplying 
plants with their mineral aliment. 

Clay intervenes no more directly than humus in 
vegetable nutrition. Nevertheless, its presence in ara- 
ble land is of unquestionable utility. Clay is a hydrat- 
ed silicate of alumina, retaining its water with great 
persistence, forming with it a very plastic paste, which 
serves to fabricate pottery. Its presence in the soil 
imparts consistence to it, diminishes its permeability, 
and maintains its coolness by retarding the passage of 
water. Like humus, clay fixes ammonia by a kind of 
capillary affinity, but it also possesses this property 
with regard to all saline solutions. By its agency the 
soluble salts resist flowing waters ; still more, it re- 
moves from highly charged saline solutions a much 
larger quantity of salts, and yields them up again to the 
water when it arrives in sufficient quantity. In a very 
fertile soil, that is to say, one much charged with sol- 
uble salts, when little water is present, the solution it 
produces might attain to such a degree of concentra- 
tion as to become injurious to plants. 



46 LECTURES ON AGRICULTURE. 

In this case, the clay, by appropriating the greater 
part of the salts, sufficiently weakens the solution. If, 
on the contrary, abundant rain falls, the clay gives up 
what it had previously taken, and thus re-establishes 
the equilibrium between seasons of drought and rainy 
weather. 

In these circumstances, the clay acts as a sort of 
automatic granary, which, out of its abundance, stores 
up superfluous aliments to distribute them again when 
scarcity prevails. It regulates the strength of the ali- 
mentary solution, as the fly-wheel of a steam-engine 
regulates its motion. 

As for the sand, it forms part of all soils, of which 
it is the essential constituent. It communicates to the 
soil its principal physical properties, and its permea- 
bility to air and water. It tempers the properties of 
the clay, and by its association with it realizes the con- 
dition most favorable to the development of plants. 

We have studied the inert elements of the soil, those 
which enter into its composition to at least 99 per 100, 
but which, nevertheless, concur in vegetable produc- 
tion only by their physical properties. It now remains 
for us to examine the elements which exist in but very 
slight proportions in the soil, but of which the part 
played is of first importance in the life of plants, since 
without them vegetation is impossible. 

Here, as with the organic elements, we commence 
by removing from the discussion the principles which 
are found in sufficient quantity in all soils, and of 
which, consequently, agriculture has no need to con- 
cern itself. For this reason we pass by, in silence, 
silica, magnesia, iron, manganese, chlorine, and sul- 



LECTURES ON AGRICULTURE. 47 

phuric acid. Phosphate of lime, potassa, and lime, 
remain. These are the essential minerals, such as, 
associated with a nitrogenous substance and added to 
any kind of soil, suffice to render it fertile. With them 
we can actually fabricate plants. 

At the commencement of my experiments, fifteen 
years ago, struck with the weakness of the old chem- 
ists with regard to the problems raised by vegetation, 
a weakness which I shall account for in my next lec- 
ture, I decided upon attempting a new method. The 
soil could not be known with accuracy, for chemical 
analysis had completely failed in ascertaining its com- 
position. I resolved to substitute for it an artificial 
mixture, all the elements of which were clearly de- 
fined. In this way I arrived at producing vegetation, 
in pots of china biscuit, with calcined sand and per- 
fectly pure chemical products. 

In these ideal conditions I instituted the four fol- 
lowing experiments : 

1. Calcined sand alone. 

2. Calcined sand with the addition of a nitrogenous 
substance. 

3. Calcined sand with minerals only (phosphate of 
lime, potassa, and lime). 

4. Calcined sand with the minerals and a nitrogen- 
ous substance. 

I sowed on the same day, in each pot, 20 grains 
of the same wheat, weighing the same weight, and 
kept the soils moist with distilled water during the 
entire duration of vegetation. At the harvest I ob- 
served the following facts: 



48 LECTURES ON AGRICULTURE. 

In the sand alone the plant was very feeble ; the 
crop dried weighed only 93 grains. 

In the nitrogenous substance alone, the crop, still 
very poor, was however better ; it rose to 140 grains. 

In the mineral alone, it was a little inferior to the 
preceding; it weighed 123 grains. 

But with the addition of the minerals and the nitro- 
genous substance, it rose to 370 grains. 

From this first series of experiments we conclude 
that each of the agents of vegetable production fulfils 
a double function : 

1. An individual function variable according to its 
nature, since the nitrogenous matter produces more 
effect than the minerals, and as either, employed sep- 
arately, raises the yield above what the seed could 
produce by itself in pure sand. 

2. A function of union, since the combined effect 
of the nitrogenous substance and the minerals is very 
superior to what each of these two agents produces 
separately. 

But it is not sufficient to prove the relation of de- 
pendence which exists between the action of the nitro- 
genous matter and the minerals, taken en masse; we 
must take account of the special action of each of them. 
Let us then institute new experiments, in which we 
associate variable mineral mixtures with a nitrogenous 
substance, always the same, and employed in the same 
quantity. 

Let us commence by suppressing, among the min- 
erals first employed, the phosphate of lime, and in its 
stead associate, with the nitrogenous matter, a mixture 
composed only of lime and potassa. 



LECTURES ON AGRICULTURE. 



49 



In these new conditions, vegetation is not possible. 
The seeds germinated and scarcely arrived at 4 inches 
in height ; the plants withered and died. A mixture 
cf potassa and lime is therefore injurious to vegetation. 
To make it useful, phosphate of lime must be added. 
Do you wish to prove it? Make a fresh experiment 
with the same agents and a trace of phosphate of lime, 
0.01 grains in 1000 grains of soil, and you will obtain 
a plant, — meagre, it is true, — but which does not 
wither and die. When the phosphate of lime is in 
sufficient quantity, the crop rises to 370 grains, as be- 
fore stated. 

There exists, then, between the phosphate of lime 
on the one part, and the potassa and lime on the other, 
a relation of unity analogous to that which we have 
shown to exist between nitrogenous matter and min- 
erals. To render an account of the part played by po- 
tassa, let us make a fresh experiment, from which we 
will banish this alkali, and in which, consequently, the 
soil will be fertilized with the nitrogenous matter and 
a mixture of lime, and phosphate of lime. 

Here the plant does not die, but the crop is inferior 
to that given by nitrogenous matter alone ; it descends 
to 123 grains. Potassa is then an indispensable ele- 
ment, in a less degree, however, than phosphate of 
lime, since its absence does not, as with the preced- 
ing, cause the death of the plants. 

Seeing that soda replaces potassa in most industrial 
uses, we inquire if it might not do the same with re- 
spect to vegetation. Experiment has defeated this 
hope. In the absence of potassa, soda exercises no 
4 



5<D LECTURES ON AGRICULTURE. 

influence upon the yield, which remains just the same, 
whether it intervenes or not. It is then indisputable 
that, with regard to wheat, potassa is of the first neces- 
sity ^ and that soda cannot be substituted for it. 

It remains to explain the part played by lime. Here 
the question becomes much more complicated. The 
method we employed just now, and in which we 
made only pure and artificial products to enter, leads 
us to results of little importance only. 

An experiment made with nitrogenous matter, phos- 
phate of lime, and potassa only, gave a crop of 340 
grains, while we obtain 370 grains with the co7nflete 
manure, by which I understand — the mixture of ni- 
trogenous matter and the three essential minerals : 
phosphate of lime, potassa, and lime. This slight 
difference seems to indicate that lime plays only a 
secondary part. Nevertheless, agricultural practice 
obtains very good effects from it. We must then seek 
by other ways to discover what may be the nature of 
its action. 

If we substitute a mixture of sand and humus, for 
pure sand without lime, the yield remains, like the 
preceding, equal to 340 grains. In the absence of 
lime, the humus has, then, no action, either useful or 
injurious. But if we add lime (in the state of carbon- 
ate) in this same experiment, the yield immediately 
rises to 493 grains. The lime which, in the absence 
of all organic matter, influences the yield in but an 
insignificant manner, manifests, on the contrary, a very 
decisive action in the presence of humus, which pro- 
duces no effect of itself, when alone. 

There exists, then, between lime and humus a re- 



LECTURES ON AGRICULTURE. 



51 



markable relation of unity. All the experiments lead 
us to this final conclusion : that the soil, to produce 
plants, must contain, under an assimilable form, a ni- 
trogenous matter, with phosphate of lime, potassa and 
lime, and that to insure the efficacy of this latter, the 
presence of humus is indispensable. You will now 
comprehend, without difficulty, why agricultural ex- 
periments made upon soils more or less fertile, have 
not led, and cannot lead, to any general practical con- 
clusion. 

Suppose that an agriculturist had the idea of adding 
to a field abounding with phosphate of lime, a manure 
containing a mixture of nitrogenous matter, potassa 
and lime, he will obtain a magnificent harvest, — be- 
cause the phosphate of lime in the soil united to the 
matters brought by the manure, will complete the lat- 
ter, and the plants will find everything necessary to 
secure their development. 

This agriculturist will sound the praises of his ma- 
nure. Others, imitating his example, will try the same 
experiment. But if it happens that their fields contain 
no phosphate of lime, far from yielding the marvellous 
results promised, this manure will, on the contrary, 
lower the yield, for we now know that in the absence 
of phosphate of lime, a mixture of nitrogenous matter, 
potassa and lime, is injurious to vegetation. 

This example will, I think, suffice to explain all the 
mistakes that cultivators have experienced in the 
course of agricultural experiments, and to justify my 
method, which consists of removing everything un- 
known from the soil, by substituting for the latter an 
artificial mixture of definite composition. 



52 LECTURES ON AGRICULTURE. 

Now that by delicate and precise experiments we 
have arrived at the knowledge of the superior laws of 
the production of vegetables, shall we remain content- 
ed with philosophically contemplating them, and con- 
tinue to follow, as before, a blind empirical practice? 
Shall we continue without concern to exhaust the soil 
around us, and restore to it, in the form of manure, 
only a small portion of what it yields to us in the form 
of crops, ready to transfer our industry elsewhere, when 
our country refuses to nourish us, as the Arab trans- 
fers his tent and his flocks? Or shall we continue, in 
despair of the cause, to surrender ourselves blindfolded 
to the charlatanism of adulterated manures and the 
traders in an agricultural panacea? No! these truths, 
so simple and so fruitful, will quit our laboratories to 
enter into daily practice. Our industry will seek the 
elements of fertility in the vast quarries where nature 
has stored them up, and agriculture, henceforth confi- 
dent in itself and its products, will assume greater 
attractions, and come to range itself, like all other 
branches of production, under the essentially progres- 
sive banner of supply and demand. 

Such is the prospect opened by science to agricul- 
ture, and which it remains for us to sound the depths. 
But before attempting, with reference to arable land, 
the problem we propose to solve under ideal conditions, 
we must study the soil itself, and learn how to ascertain 
its elements of fertility — in a word, to analyze it. In 
my next lecture I shall explain to you why chemists 
have failed, and shall show you how, more fortunate 
than my predecessors, I have arrived at success my- 
self. 



LECTURE FOURTH. 



ANALYSIS. 

Science chiefly concerns itself with the Elements of Bodies as 
modified by Association, and the various Forms of which 
this Association is susceptible. — Chemical Analysis inad- 
equate to the Analysis of Soils in discovering the Causes 
of Fertility. — The Synthetic Method teaches that Analysis 
need concern itself with Four Elements only. — The Soil 
consists of Mechanical and Assimilable Agents, the latter 
being Organic and Mineral. — Review of the Analytical 
Labors of Chemists ; Causes of their Failure. — The three 
most important Questions remained unsolved : " How much 
Wheat will a given Soil produce? " " What will be the best 
Manure for it, and how much must be employed ? " " How 
long will its Effects continue?" — The Elements of Fertil- 
ity in a Soil must exist in an assimilable Form, so that 
Water can dissolve them and convey them to the Interior 
of the Plant through the Spongioles of the Roots. — The 
best Reagent in analyzing Soils is the Plant itself, as is 
shown by the Result to the Crops of suppressing one of 
the four essential fertilizing Agents. — This new Method 
banishes all Hypothesis, and adapts itself to every want of 
Cultivation. — Result of Experiments. 



SINCE chemical analysis. has arrived at the discov- 
ery of the composition of most of the materials 
that render service to mankind, science has become 

53 



54 LECTURES ON AGRICULTURE. 

accustomed to regard among the properties of bodies 
only that of their elements modified by association, 
and the various forms of which this association is 
susceptible. 

This theoretical view is more and more verified in 
proportion as chemistry penetrates deeper into the 
study of nature : so much so that, nowadays, the idea 
of the chemical elements, such as proceeded from the 
researches of the immortal Lavoisier, governs all the 
sciences which are occupied with matter and its trans- 
formations. The science of vegetation cannot remain 
a stranger to this movement, and the attempts direct- 
ed to the end of bringing it under the common law 
have not failed. No sooner had chemical analysis 
begun to assume a scientific character, than it attempt- 
ed to discover in the soil the causes of its fertility. But, 
too weak as yet to accomplish such a task, it exhaust- 
ed itself in impotent efforts, and we may say that, not- 
withstanding the progress which has brought this 
young science rapidly to the maturity we witness at 
the present day, it has none the less remained unfruit- 
ful with regard to agricultural problems. 

The reason of this is very plain. Suppose we re- 
quire of a chemist the analysis of a mineral containing 
traces of gold, without informing him of the presence 
of this precious metal in it. His attention will be given 
to each of the predominating elements ; as for the gold, 
it will escape his researches. If, on the contrary, you 
point out to him the element you desire to prove the 
presence and quantity of, the chemist will proceed 
quite differently. He will begin by removing from 



LECTURES ON AGRICULTURE. 55 

his analysis all unimportant substances. Concerning 
himself only with the gold you have named to him, he 
will succeed in concentrating it in a very small quan- 
tity of matter, where its presence will be manifested 
and its determination easy. 

When engaged in the analysis of soils, chemists 
have hitherto found themselves in the first of these 
two alternatives. Ignorant of what the elements of 
the soil were which played an important part in the 
formation of vegetables, they attributed this faculty to 
the agents which predominated in the soil examined. 
The direction of their analyses thus varied according 
to the various hypotheses which led them to a more or 
less happy intuition, or to the assertions more or less 
well founded of agriculturists. 

To change this state of things, we must substitute 
for these hypotheses a certain knowledge which indi- 
cates, with absolute precision and rigor, the elements 
which analysis must occupy itself with, and if you will 
call to mind the facts established at the last lecture, 
you will have no difficulty in admitting that this 
knowledge is at the present time in a very promising 
condition. 

For we know that there exist in the soil materials 
which do not enter into vegetable production except 
as a support to the roots, thus realizing a kind of re- 
cipient for the useful elements. We designate them 
by the name of mechanical agents. 

We call assimilable agents all those which, at a 
given moment, penetrate the plant in the state of aque- 
ous solution, to form afterwards an integral part of its 
tissues. 



56 



LECTURES ON AGRICULTURE. 



Lastly, we rank in a third class the assimilable agents 
in reserve, all the organic and mineral debris which 
contain useful elements, but which cannot give them 
up to water until after a previous decomposition. 

We are thus led to the following classification of 
the elements of the soil, a truly natural classification, 
as it rests upon the facts which we have derived from 
the results of cultivation itself. 



COMPOSITION OF A FERTILE SOIL. 



I. Mechanical Agents 



Active Assimilable 
Agents . . . . 



Assimilable Agents 
in reserve . . . 



Organic 



Mineral 



fHun 
. | Nitn 

I Ami 



f Sand. 
\ Clay. 
I Gravel. . 
umus. 
•ates. 

moniacal Salts. 
Potasssa. 
Soda. 
Lime. 
Magnesia. 
Soluble Silica. 
Sulphuric Acid. 
Phosphoric Acid. 
Chlorine. 
Oxide of Iron. 
Oxide of Manganese, 
f Undecomposed organic matters. 
^Undecomposed fragments of rocks. 



It is by ignoring or mistaking this classification that 
the most skilful chemists have failed to arrive at any 
useful result. Still, it will not be uninteresting to pass 
their attempts in review. 

Sir Humphrey Davy, one of the greatest chemists 
England has produced, conceived the idea of submit- 
ting to analysis various soils celebrated for their fertil- 
ity, hoping thus to arrive at the recognition of some- 



LECTURES ON AGRICULTURE. 



57 



thing common between them, some preponderating 
element to which their agricultural properties might 
legitimately be attributed. 

The following are the results at which he arrived : 















— u 


01 




T3 

a 









O re 


§ 




3 










































s 
.2 

c/3 


CO 


c 

e 

< 


IP 


2 c 
U 





ia re 
C/2 


IS 

■a 

c/3 


Hop land 


66.3 


5-2 


3-3 


4.8 


8.0 


1.2 


8.0 


O.^ 


Turnips 


88.9 


i-7 


1.2 


7- 


80 


0.3 


O.6 


o.t; 


Wheat 


60.0 


12.8 


11. 6 11. 2 


8.0 


0.3 


4.4 


o.<> 


Very fertile 


60.0 


16.4 


140 5.6 


8.0 


1.2 


2.8 


0.=; 


Very good quality 


83-3 


7.0 


6.8 0.7 


80 


0.8 


1.4 


0^ 


Excellent pastuiuige . 


9.1 


12.7 


6-4 57-3 


8.0 


1.8 


12.7 


0.5 



By an inspection of this Table we perceive how lit- 
tle experience confirms the views of this celebrated 
chemist. He only proved dissimilarities between all 
the soils examined, and yet all were fertile. 

How can such a failure be explained? If Davy 
had been aware of the facts which I have explained 
to you at our previous lecture, and with that summary 
classification which has engaged our attention, it 
would have been easy for him to see that, in his anal- 
yses, he had taken no account of the agents which 
alone assure the fertility of the soil. He makes no 
mention of potassa, phosphate of lime, or nitrogenous 
matters, principles without which production is im- 
possible. Davy analyzed the ore, without concerning 
himself with the precious metal. But could it have 
been otherwise at the date of his labors? Chemistry 



58 LECTURES ON AGRICULTURE. 

had then only just got out of its leading-strings, and 
possessed but very vague notions of the life of plants, 
the result of empirical observations which no rational 
union had yet arranged. 

Again, far from perceiving the true cause of Davy's 
want of success, the science of his day drew a very 
singular conclusion from his labors. It was thought 
that the elements of the soil had no influence upon its 
fertility, and that if it were desired to find a reason for 
its agricultural qualities it must be sought in the study 
of its physical properties. 

This false interpretation has not been without its 
advantage to science. It has caused the production 
of extensive works on the part of physicists, and par- 
ticularly from Schubler, who specially applied himself 
to researches of this kind. 

The result was a profound knowledge of the me- 
chanical properties of the dominant agents of the soil, 
properties the influence of which, although secondary, 
nevertheless merit a serious examination. 

The labors of the physicists were scarcely a whit 
happier than those of the chemists, and the problem 
remained intact in spite of these two series of at- 
tempts. As usually happens, after excessive contra- 
dictions, they next attempted to reconcile the two 
methods, and M. Berthier undertook analyses in 
which he endeavored to take account of both the 
physical properties and the chemical composition of 
soils. 

We give an example on the next page. 



LECTURES ON AGRICULTURE. 59 

SOIL OF THE VINEYARDS OF POMARD 
(COTE D'OR). 

No. 1. No. 2. 
Quartz remaining upon the hair sieve, 2.6 2.5 

Quartz remaining upon the silk sieve, 1.4 2.0 

Quartz obtained by levigation, . . . 8.5 4.6 

Exceedingly fine Quartz, 17.5 13.3 

Combined Silex, 10.2) clay, 7 8 7 

Alumina, 5- 1 b I 5-3 3-9 b ' 

Hydrate of Iron, 98 7.4 

Calcareous Stone remaining upon > Q 

the hair sieve, $ 3 ° 3 4 

Ditto remaining upon the silk sieve, . 2.9 00 

Calcareous Stone in fine grains, . . 7.8 2.2 

Ditto in exceedingly fine grains, . . . 11. 3 17.8 

Organic matters, 1 2.0 

101.1 102.0 

After the labors of M. Berthier, science was not 
more advanced than before, and the most skilful chem- 
ist was still without a reply to the three questions 
which interested agriculturists in the highest degree : 

1. How much wheat will such a soil produce? 

2. What will be the best manure for it, and how 
much must be employed ? 

3. How long will its effect continue? 

Nowadays science seems to have made a step. In- 
stead of contenting itself with measuring the mechani- 
cal elements of the soil, it determines with the great- 
est care all the elements of fertility : lime, magnesia, 
the alkalies, phosphoric acid, nitrogen, &c, as, more- 
over, we may convince ourselves by the following 
example : (See page 60.) 

But these laborious and complete analyses, in which 
nothing is forgotten, are still useless to agriculture, and 
cannot, any more than the preceding, reply to the 
questions that essentially concern it. 



6o 



LECTURES ON AGRICULTURE, 



ANALYSIS OF A SOIL IN THE ENVIRONS OF 
CHALONS-SUR-MARNE. 



Fine Matters 



i. Mechanical Analysis. 
. . . 52.50 I Sand and Gravel 
2. Chemical Analysis. 



42.25 



Organic Matter .... 1.80 

Hygrometric Moisture . 2 70 

Water of Combination . 5.92 

Carbonic Acid 33- 2 ° 

Quartz Sand 3.10 

Clay 6.00 

Attackable Silica . . . 3.10 

Oxide of Iron 2.00 

Alumina 0.15 



Lime 40.50 

Magnesia traces. 

Alkalies 0.38 

Sulphuric Acid .... 0.28 
Phosphoric Acid . . . 0.12 
Nitrogen and Chlorine. traces. 



99-25 



In fact, for a soil to be fertile, it is not sufficient that 
it contains potassa, phosphoric acid, lime, and nitro- 
gen : these agents must also exist in an assimilable 
form ; that is to say, in a state in which the water in 
the soil can dissolve them, to convey them into the 
interior of plants through the spongioles of their roots. 

Suppose that a soil contains a feldspathic sand in- 
stead of a quartz sand. Chemical analysis would 
show the presence of all the agents useful to vegeta- 
tion, and still this soil would be of a desolating steril- 
ity ; for, in feldspar, these bodies are combined in 
silicates which water cannot dissolve. 

Not only, then, is it necessary to determine the 
presence and quantity of the useful elements, but 
analysis, to be fruitful, must also occupy itself with 
the kind of combinations in which they are engaged. 
I have myself sought the solution of the problem in 



LECTURES ON AGRICULTURE. 6 1 

this direction ; and, to remove from the first attempt 
that portion of the soil which can contribute nothing 
to its fertility, I have commenced by washing the soil 
with distilled water, hoping to arrive, by evaporating 
the liquid obtained, at concentrating in a small bulk 
the only principles which it was necessary to take 
notice of. 

Submitted to this treatment, the soil of Vincennes 
yielded to water only a very little potassa, and no 
phosphates at all. Nevertheless, three successive crops 
of wheat have extracted 188 lbs. of phosphoric acid and 
2036 lbs. of potassa. The exhaustion by distilled wa- 
ter is therefore mucn less efficacious than the natural 
exhaustion. In fact, in the soil the solvent power of 
the water is greatly increased by the carbonic acid 
with which it is constantly charged by the salts it dis- 
solves, and by the time during which it acts. 

With the view of approaching nearer to the condi- 
tions of solution in nature, I have attempted to exhaust 
the soil by water slightly acidulated with hydrochloric 
acid. But then I fell into the opposite extreme. 
While the three crops of wheat exhausted the soil and 
extracted from it only iSS lbs. of phosphoric acid, acid- 
ulated water indicated 1000 lbs. the acre. In fact, 
chemistry has not been more powerful in my hands 
than in those of my predecessors, and the failure must 
be attributed to the insufficiency of the methods of 
exhaustion at command. 

Must we, then, despair of ever being able to analyze 
the soil in a brief space of time by means of a labora- 
tory susceptible of defining its agricultural properties 



62 LECTURES ON AGRICULTURE. 

with certainty? I do not think so. The problem, 
although not hitherto solved, does not appear to be 
insoluble. The whole difficulty consists in extracting 
from the soil everything that plants are susceptible of 
drawing from it, without going beyond what they do 
themselves. 

Perhaps dialysis, from which Mr. Graham has de- 
rived such admirable results, may, by its application 
to the study of soils, lead to more useful data than 
those I have criticised. But these methods are not 
yet instituted, and I speak of them only as things 
hoped for. 

Leaving aside, then, the chemistry of the laboratory, 
the present weakness of which we fully recognize, and 
taking up the results I have previously explained to 
you, we deduce a more certain method, one in which 
we employ no other reagent than the plant itself. 

If you recall to mind what I said in our last lecture, 
you will remember that four essential agents suffice to 
assure the fertility of soils, and that the suppression of 
one of them lowers the yield to a very important ex- 
tent. Now, conceive a soil naturally provided with 
phosphates : is it not evident that the suppression of 
phosphates in the manure supplied to it will produce 
no bad effect? Reciprocally, whenever the manure 
without phosphates produces a crop equal to that from 
a manure which does contain it, we shall be justified 
in admitting that the soil is naturally provided with it. 

Do you wish to be similarly instructed with regard 
to lime, potassa, and nitrogenous matter? Cultivate 



LECTURES ON AGRICULTURE. 6$ 

the same soil with manure deficient in lime, potassa, 
and nitrogenous matter, and, according as they pro- 
duce good or bad crops, draw your conclusions as to 
the presence or absence of these agents of fertility. 

This new method banishes all hypothesis, since it 
rests upon the following facts, proved by experience, 
namely : 

i. That the association of minerals and an assimi- 
lable nitrogenous matter produces good crops every- 
where ; while isolated, these agents are always inert. 

2. That lime produces a useful effect only in pres- 
ence of humus. 

3. That lime and humus produce great effects only 
in a soil provided with minerals and nitrogenous 
matter. 

This method adapts itself to all the wants of culti- 
vation, since it is sufficient to scatter a few handfuls 
of a fertilizing manure upon a field to indicate, at the 
time of harvest, what the soil contains, what it wants, 
and, consequently, what must be added to it to render 
it fertile. 

Lastly, it is essentially practicable, as it requires no 
difficult manipulation, no apparatus, and employs 
only the usual processes of cultivation. 

It now remains for us to examine to what degree it 
is precise and exact, and with that to put it to the test 
of experiment. 

The following are the results obtained in three dif- 
ferent soils, compared with those given by calcined 
sand under similar conditions. 



6 4 



LECTURES ON AGRICULTURE. 







i 


2 


COMPLETE MANURE. 




3 


4 


5 


6 


7 




I 


3 aJ 

2 3 
*! C 
• - rt 


s § 

as 


3 

lis" 


■5 s 

EC 2 


O $ 

\c 


3 . 

c <u 
S 3 


.a 3 


Calcined 
Sand. 


' 6 


24 


8 


O 


7 


22 


32 


Soil from 
Gascogne. 


} 


55 


32 


9 


6 


8 


22 


32 


Soil from 
Bretagne. 


} 


4 


29 


16 


9 


18 


22 


32 


Soil of 
Vincennes 


} 


ii 


35 


20 


28 


28 


32 


32 



The soil from the landes of Gascogne, without 
manure, was not more fertile than calcined sand : with 
complete manure, its yield was equal to that of cal- 
cined sand with humus and complete manure ; this 
soil therefore contained humus. 

Reasoning in the same manner with regard to the 
elements, we see that it contains neither nitrogenous 
matter, nor potassa, nor lime, since, in their absence, 
it is not more fertile than calcined sand. On the 
other hand, it contains traces of phosphoric acid, for 
in the experiment where it was not added, it yielded 
a light crop, while in the sand the plants invariably 
perished. 

As for the soil of the landes of Bretagne, these ex- 
periments show it contains humus, a little nitrogenous 
matter, a little potassa, and very small quantities of 
phosphates. 

The soil of Vincennes, examined in the same man- 



LECTURES ON AGRICULTURE. 



65 



ner, showed itself to be rich in humus, phosphates, 
potassa, and lime, but poor in nitrogenous matter. 

These are positive data, which we can employ in 
fertilizing soils. Let us now see to what extent they 
were verified in practice on a large scale. (Seep. 66.) 

This table shows that, without phosphates, the crop 
was nearly equal to what it was with a complete ma- 
nure ; that without potassa it sensibly diminished, and 
that without nitrogenous substances it was very infe- 
rior. These results are exactly like those derived 
from experiments on a small scale. But do you wish 
to see with what precision these results agree? Sup- 
pose the crop with complete manure equal to 35, as 
it was on the small scale, and calculate the others with 
reference to that. 

You will thus be led to the following comparison : 





6% 


COMPLETE MANURE. 




... 3 

5 


3 ri 
O " 

•5 5 


2 

•§■& 
> 

Oh 


Cultivation on a small scale . . 
Cultivation on a large scale . . 


35 
35 


20 
21.7 


28 

30 


28 
32 



I will ask you, is it possible to attain to a more per- 
fect concordance, and is it not the most satisfactory 
proof of the excellence of the method I have commu- 
nicated to you? 

The plant, therefore, becomes in our hands one of 
the most perfect instruments of analysis, the only one, 



66 



LECTURES ON AGRICULTURE. 







Lbs. 
16.282 


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LECTURES ON AGRICULTURE. 67 

in the present state cf science, susceptible of making 
known, practically, the composition of soils. But I 
shall give to this proposition a still more striking 
demonstration, by showing you to what extent this 
test goes. 

We have seen that, in calcined sand and complete 
manure without phosphates, we succeed in causing 
the death of plants. In the soil from the landes of 
Gascogne the same compound gave a crop equal to 6, 
which proves, as we have stated, the presence of small 
quantities of phosphates in the soil. 

To 1 cwt. of calcined sand and complete manure 
without phosphates, add only T ^ F of 1 per 100 of 
phosphate of lime, that is to say, TuihsirG of the weight 
of the soil. Immediately the yield rises to 6, as in 
the soil of the landes of Gascogne. 

We are then correct in saying that vegetation re- 
veals to us with certainty, in this soil, the presence 
of -nnrWu °f phosphate of lime. 

What chemical process, let me ask, can attain to 
such limits? 

The accuracy of this method, in relation to the 
other elements, is no less remarkable. tgv-utj of 
potassa cause the yield to pass from 8 to 32 ; y^^ 
of lime in presence of humus raises it from 12 to 24. 

We are then assuredly in possession of a means of 
analysis, the perfection of which yields in no respect 
to the most delicate processes of the chemical labora- 
tory, the indications of which are verified exactly by 
cultivation on a large scale, capable, consequently, of 
throwing a sure light upon agricultural operations. 



68 



LECTURES ON AGRICULTURE. 



To put it into practice, the agriculturist will only 
have to reserve some square plots in a field, to which 
he will give complete and partial manures of the fol- 
lowing composition for the surface of an acre : 





6 

"a 
S 
o 
O 




— « 


"3 « 
O <g 

•►r 


H 


3 . 
« 




Lbs. 


Lbs. 


Lbs. 


Lbs. 


Lbs. 


Lbs. 


Phosphate of Lime 


352 


352 




352 


. . . 


352 


Carbonate of Po- > 
tassa ) 


352 


352 






352 


352 


Quicklime .... 


132 


132 




132 


132 




Nitrate of Soda, ) 
(nitrogenous matter,) \ 


488 




488 


48S 


4S8 


4S8 



At the harvest he will carefully note the results ob- 
tained, and for the following year he will fix upon that 
which his soil requires, and, consequently, upon that 
which he must give to it to restore its original fertility, 
and to fertilize all the plots, if they do not give good 
results. 

For several years past, geologists have endeavored 
to prepare maps in which they represented, by partic- 
ular tints, soils of different geological construction. 
These maps assumed to come to the aid of the agri- 
culturist, but they completely failed, like the method 
of analysis upon which they were founded. By the 
processes I have explained to you, we can now ascer- 
tain the real agricultural properties of soils, and con- 
sequently resume the task of the geologists with the 
aid of data from cultivation itself. We shall in this 



LECTURES ON AGRICULTURE. 



6 9 



manner arrive at constructing true agricultural maps. 
What is required? Some experimental fields analo- 
gous to those at Vincennes, disseminated over the 
surface of France, upon lands belonging to the princi- 
pal geological types. The centralization of the results 
obtained will permit of the drawing up of an exact in- 
ventory of the agricultural resources of the Empire. 

To give you some idea of the benefit which may be 
derived in this object, from our own method, it will 
be sufficient for me to compare the results of the farm 
at Vincennes with those obtained in England by 
Messrs. Laws and Gilbert, who also have instituted, 
at their farm at Rothamstead, experiments in cultiva- 
tion with manures of known composition. 

MESSRS. LAWS AND GILBERT'S RESULTS. 



YEARS. 




Mean. . 



Complete Manure 




I5,OIO 



Minerals without 

Nitrogenous 

Matter. 



Lbs. 




10,208 



Nitrogenous 

Matters 
with Minerals. 




12,324 



70 LECTURES ON AGRICULTURE. 

RESULTS AT VINCENNES. 
Mean . . . 17.992 10.57 12.824 

With complete manure the mean yield is nearly the 
same ; without nitrogenous matter the yield at Roth- 
amstead is very inferior. Messrs. Laws and Gilbert's 
land, therefore, contains less nitrogenous matter than 
that of Vincennes. 

Without minerals, the yields are very nearly alike ; 
the two soils have, therefore, nearly the same mineral 
richness. There is a slight advantage for that of 
Vincennes. 

Thus you perceive that, armed with our method, we 
can make a retrospective analysis of all the soils of 
which we possess information of the exact culture ; 
still better when the documents collected for the pur- 
pose are as complete as possible. 

But it will not be sufficient to point out to you the 
agents by means of which we can analyze the soil and 
fertilize it. To give you the power to manage these 
valuable fertilizers, I must also tell you under what 
form they must be administered to plants, and from 
what sources of human industry they can be provided. 
This will form the subject of my next lecture. 



LECTURE FIFTH. 



ANALYSIS. 

The Ideal Manure, or Manure far excellence. — Comparison 
between the Composition of Ideal and Practical Manure. — 
Definition of Nitrogenous Matter. — Sources from whence 
Nitrates may be obtained. — From the Atmosphere : From 
the Ammoniacal Salts obtained in Coal-gas Manufacture : 
From Sewage Waters. — The Hydrochlorate the best Form 
of Ammonia to be employed. — Value of Nitrate of Potassa, 
and of Nitrate of Soda. — Animal and Vegetable Refuse a 
Source of Nitrogen. — The Phosphates: in Chalk, Nodules, 
Coprolites, Apatite, Osseous Breccia, Sugar Refiner's Char- 
coal, Bones, Guano. — Phosphate of Lime. — Potassa, Ni- 
trate, Carbonate. — New Sources for the Supply of Potassa, 
from Sea-water and Felspars. 



I HAVE. announced to you for to-day's lecture, the 
particular study of the agents we can employ to 
fertilize or analyze the soil. But before entering upon 
details, it is necessary to note the point at which we 
have arrived, and to explain to you the idea of manure 
such as it is when disengaged from the principles I 
have previously laid down. 

We have shown that the fertility of soils depends 
on the presence, in their substance, of the elements 

7* 



72 LECTURES ON AGRICULTURE. 

which we have called active assimilable agents. From 
this it evidently results that, to render a barren soil 
fertile, it will suffice, in most cases, to add the whole 
of these elements to it. This is, in fact, what the ex- 
periment with calcined sand proves, where such a 
mixture realizes conditions of fertility equivalent to 
those of a good soil. We may say, then, that this 
mixture is the ideal mixture, the manure par excel- 
lence. 

But when we work upon arable land, it is impossi- 
ble that it should not already contain a portion of the 
necessary elements. Some, such as iron and manga- 
nese, of which plants take up only infinitesimal 
quantities, exist almost everywhere. Generally, then, 
there need be no fear of their deficiency. We may, 
therefore, dispense with introducing them into a prac- 
tical manure. 

We also banish from its composition all the agents 
of which the mode in action is only imperfectly known 
to us, or in which we are still ignorant of the form 
susceptible of manifesting their influence. It is for 
this reason that we exclude soda, magnesia, sulphuric 
acid, and chlorine. 

Science, from its nature, is essentially progressive, 
and I do not pretend that I possess the whole truth, or 
that nothing remains to be discovered. Far from this. 
I hope, on the contrary, I may be permitted to add 
fresh knowledge to that which I have already impart- 
ed to you, and it is with this aim that I actively pursue 
my researches. Let us, then, banish every exclusive 
idea, and construct a manure as perfect as the science 



LECTURES ON AGRICULTURE. 



73 



from which it is deduced, and content ourselves with 
composing it of elements, the action of which is wholly 
definite, the useful form perfectly known, and of which 
plants require important quantities. This practical 
manure will represent all that we can obtain most per- 
fect in the present state of our knowledge, it will be 
sufficient in the generality of cases for all the require- 
ments of cultivation, and if the future be called to 
make useful additions, we can at least assert that we 
shall have nothing to retract. 

These considerations lead us to the conclusions 
expressed in the following tables 



Active As- 
similable 
Agents. 



Organ 



Mineral. 



Ideal Manure. 

Humus. 
f Nitrates ( 

ic. 1 Ammoniacal Salts. \ 
' Potassa. 

Soda. 

Lime. 

Magnesia. 

Soluble Silica. 

Sulphuric Acid. 

Phosphoric Acid. 

Chlorine. 

Oxide of Iron. 
V. Oxide of Manganese. 



Practical Manure. 

Nitrogenous 

Matter* 
Potassa. 

Lime. 



Phosphate. 



Among the constituents of the practical manure 
figures lime, which is easily procured everywhere, and 
with the history of which nearly everybody is ac- 
quainted. I may therefore dispense with repeating it 
to you, preferring to reserve my explanations for less 
known materials, and which it is less easy to obtain. 

I call nitrogenous matter every principle which in- 
cludes nitrogen among the number of its elements, and 



74 LECTURES ON AGRICULTURE. 

capable of supplying it to vegetation. This includes 
the remains of all beings that have lived. Buried in 
the soil, they undergo slow decomposition, in conse- 
quence of which their nitrogen separates partly in the 
state of carbonate of ammonia or of nitric acid. These 
substances are retained in the soil by humus or by 
clay, and water afterwards dissolves them gradually 
and conveys them into the interior of vegetables. But, 
as nitrogenous matters of animal or vegetable origin 
are useful only after being transformed into ammonia- 
cal salts or nitrates, there is every advantage in having 
recourse to these products ; this is why, from the pres- 
ent point of view, we give them also, by extension, 
the denomination of nitrogenous matters. 

I have already shown you the efficacy of the nitrates 
and of the ammoniacal salts, in our second lecture, 
and I need not return to the subject, but limit myself 
to making known to you the sources from whence we 
may obtain these compounds. 

The great natural store of nitrogen is the atmos- 
phere. We have seen that vegetation in general en- 
joys the faculty of drawing from it the greater portion 
of the nitrogen it assimilates. The idea of imitating 
nature, and of procuring nitrogenous compounds by 
causing the nitrogen of the air to enter into combina- 
tion, has for a long time presented itself to the minds 
of chemists. Unfortunately, free nitrogen possesses 
only very feeble affinities, which renders the problem 
thus put by chemistry extremely difficult of solution. 
Recently, however, Messrs. Sourdeval and Margue- 
rite have succeeded in producing ammonia with the 



LECTURES ON AGRICULTURE. 75 

nitrogen of the air by a very interesting reaction, but 
still too expensive for it ever to become an important 
source. These chemists made atmospheric nitrogen 
pass over carbon impregnated with baryta, at a very 
high temperature. In this manner cyanide of barium, 
BaC 2 N, is produced, the nitrogen of which is convert- 
ed into ammonia by a current of steam from water. 
This remarkable experiment realizes the scientific so- 
lution of the problem, but it does not give the eco- 
nomic solution. 

For many years past the manufacture of coal gas 
has thrown very important quantities of ammoniacal 
salts into commerce. We know that coal contains 75 
per 100 of nitrogen, which is partially disengaged 
during its distillation. This ammonia is condensed 
in acid waters, the evaporation of which furnishes am- 
moniacal salts. This course is certainly not to be 
despised, but it is far from being sufficient. 

England consumes annually 1,000,000 tons of coal 
in the manufacture of gas. From this result about 
10,000 tons of ammoniacal salts, which scarcely suf- 
fice to supply 50,000 acres of arable land with nitro- 
genous manure. If we remember that the territory 
of France contains about 125,000,000 acres of culti- 
vated land, we shall have an idea of the importance 
of the outlet which agriculture presents to ammoniacal 
salts, and of the insufficiency of gas manufacture to 
supply this consumption. It must not be forgotten, 
however, that this is a source scarcely turned to full 
account, which rests upon a manufacture very rich in 
its future promise, and which would receive important 



*j6 LECTURES ON AGRICULTURE. 

developments if the production of coke in closed cham- 
bers were generally substituted for its manufacture 
under the open sky. 

The ammoniacal salts arising from the distillation of 
coal, merit, besides, all our sympathies, for they restore 
to the vegetation of our times a portion of the nitrogen 
which has contributed in former times to the immense 
vegetable formations of which coal presents us the 
debris. They thus place at the disposal of human in- 
dustry considerable quantities of combined nitrogen, 
which, in this manufacture, remain entirely lost, buried 
in the bowels of the earth. 

There exists another very abundant source of am- 
monia : in sewage waters. These waters have for a 
long time been the object of a certain manufacture. 
They are distilled with lime in large leaden retorts. 

The ammonia disengaged is collected in diluted 
hydrochloric acid, the evaporation of which yields sal 
ammoniac. But the heat lost at the end of each oper- 
ation raises the cost of this product too high for the 
manufacture to become extensive. Messrs. Sourdeval 
and Marguerite have recently applied to this distilla- 
tion a continuous apparatus similar to that which ren- 
ders such great service in the manufacture of alcohol. 
By this happy innovation the cost of production has 
been greatly reduced, and these gentlemen, in a single 
manufactory, have already succeeded in manufacturing 
about 6 tons of sal ammoniac per day, which they sell 
at a very moderate price. This manufacture, which is 
susceptible of very great extension, may become a 
source of wealth to agriculture, for it will permit of 



LECTURES ON AGRICULTURE. 77 

returning to it a great portion of the combined nitro- 
gen, which it continually withdraws in the form of 
crops, and which thus accumulates in cities, where it 
is generally lost, to the great detriment of the public 
health. 

Whatever be the source of the ammonia, its hydro- 
chlorate (N,H 4 C1) appears to be the most advanta- 
geous form under which it can be employed. It has 
always given us good results. To light lands it may 
t>e given in quantities of 440 lbs., representing 1 14 lbs. 
of nitrogen, per acre. But upon strong lands this 
quantity would be excessive, unless the season were 
wet : it would cause the wheat to be laid. In such 
cases, we must reduce it to 260 or 300 lbs. at the most, 
which at the rate of 17 shillings the cwt, makes a 
manure of 375. to 47^. In sal ammoniac, nitrogen 
costs 8d. per pound. 

Instead of this salt, we can employ Peruvian nitrate 
of soda, the price of which is also 175. the cwt. Only, 
as it contains less nitrogen than sal ammoniac, it is 
dearer. The cost of its nitrogen is about is. per lb. 
Whenever, then, it is proposed to give nitrogenous 
matter only to the soil, it is best to have recourse to 
sal ammoniac. But when we wish to make it enter 
into a mixture constituting a complete manure, and 
consequently containing lime, a mixture which may 
be kept and sent to a distance, then it is preferable to 
take nitrate of soda, because under the influence of 
moisture, lime in time decomposes the sal ammoniac, 
and thus causes the loss of a portion of the useful 



78 LECTURES ON AGRICULTURE. 

To employ nitrate of soda, it suffices to scatter it on 
the soil, the same way as seed, and afterwards harrow it 
in, so as to mix it well with the upper layer of the 
soil. With sal ammoniac it is preferable to first mix 
it with two or three times its weight of moist earth, 
then leave it to dry, and spread it afterwards. By this 
method its diffusion is very uniform. 

To give nitrogen to the crops, we can also, besides 
nitrates and ammoniacal salts, have recourse to all ni- 
trogenous matters of animal or vegetable origin which 
can be procured economically, provided they are 
readily decomposed in the substance of arable land, 
without which their useful effect may be wasted for a 
long time. In the employment of these matters we 
must also take into account, that only about one-third 
of their nitrogen, separated during their decomposition 
to the elementary state, can be profitable to vegetation 
as combined nitrogen. 

Let us now proceed to the study of the phosphates. 

Phosphoric acid is widely diffused in nature : it ex- 
ists in very small proportions in most of the crystalline 
rocks, where it is in combination with alumina and 
oxide of iron. In this state it is useless to vegetation, 
as water cannot dissolve it. In the sedimentary soils, 
it presents itself, on the contrary, under a form essen- 
tially assimilable to that of phosphate of lime. But in 
general, the soil contains only traces of it, some ten 
thousandths at the most, and in many countries where 
cultivation has been long continued, the soil has be- 
come wholly exhausted of it. Fortunately there exist 
upon certain points of the globe considerable quarries 



LECTURES ON AGRICULTURE. 79 

of it, sufficiently abundant to repair the losses of the 
past, and secure the wealth of the future. 

Chalk, which forms such immense deposits, always 
contains phosphate of lime, — the proportion is much 
greater the deeper we descend. At the base of the 
cretaceous strata a peculiar mineral is met with, in 
fragments of various sizes, which contain as much as 
50 per cent, of phosphate of lime. 

This product, which is very abundant, has been re- 
cently discovered ; it is known under the name of 
nodules, and promises to yield an inexhaustible supply 
to agriculture. But there is another quite as extensive, 
and much richer, and very easily worked : this is apa- 
tite, which, in Spain, forms entire mountains, and can 
be taken from the surface by the simplest means. 
Apatite is a combination of tribasic phosphate of lime 
with an equivalent of fluoride of calcium, 3Ca,0,P0 5 
-j-CaFl. In this state the phosphate of lime is very 
assimilable, but it is easy to disaggregate this rock 
and render it accessible to vegetation. It is only 
necessary, after reducing it to powder, to sprinkle it 
with its weight of sulphuric acid diluted with an equal 
volume of water. Sulphate of lime is thus produced, 
and acid phosphate of lime, which is very soluble in 
water. 

We can treat in the same manner the nodules, and 
in general the tribasic phosphate of lime, whatever its 
origin. The acid phosphate encountering an excess 
of carbonate of lime in the soil, passes to the state of 
neutral phosphate, which is a condition most favorable 
to its absorption by plants. 



80 LECTURES ON AGRICULTURE. 

Before the discovery of the nodules, which begin to 
enter largely into practical agriculture, and of apatite, 
which has only recently made its appearance, we have 
had recourse, successively, to coprolites, a sort of 
phosphated concretion of animal origin, abundant 
quarries of which exist ; to the fossil bones found in 
caverns, and in rocks known as osseous breccia ; to 
the charcoal black of sugar refineries, and also to the 
bones in a natural state, after calcination, or after a 
previous boiling to remove the fat, which are infinitely 
superior. All these products have rendered, and can 
still render great service ; but there is another to which 
I desire more particularly to call your attention, both 
on account of the important part it has played in the 
agricultural revolution we have witnessed, as in con- 
sideration of its richness in phosphates, and of the 
abundance of its sources. This is guano. 

When this product began to be noticed, about 1804, 
no one then supposed that it was possible to find a 
substitute for the farm dung-hill. It was this that 
attracted the attention of chemists and agriculturists 
to artificial manures, and such was the state of igno- 
rance that continued to prevail till within a few years 
that the fertilizing properties of guano were exclusive- 
ly attributed to the nitrogen it contained. Whatever 
ideas were entertained of its action, the good results it 
produced, showed, also for the first time, that it was 
possible to obtain very good crops by processes that 
finally broke up the traditions of the past, and opened 
to agriculture the entirely new path of artificial 
manure. 



LECTURES ON AGRICULTURE. 8 1 

Guano forms extensive deposits upon the islands 
scattered in the Pacific Ocean, and upon the coast of 
Peru. It is supposed to be produced by the excre- 
ments of birds that feed upon fish. Its composition is 
not quite favorable to this hypothesis. It contains 
much more phosphoric acid, proportionally, than the 
excrements of birds. It therefore seems to me more 
probable that it contains both the excrements and the 
skeletons of birds. Whatever it be, guano containing 
both nitrogen and assimilable phosphate of lime, con- 
stitutes an essentially fertilizing substance. To con- 
vert it into a complete manure, it is sufficient to add to 
it potassa and lime. Guanos are not always of the 
same composition. Their richness in nitrogen varies 
from 5 to 14 per cent., and their contents in phosphates 
extend to 25 or 35 per 100. Therefore, before em- 
ploying these products, it is necessary to submit them 
to analysis, both to guard against adulteration, to 
which they are frequently exposed, and to ascertain 
the quantities that should be employed. 

Whatever the form under which we obtain phos- 
phate of lime, the proper quantity per acre is 160 lbs. 
We can previously convert it. into phosphoric acid, as 
I before stated, and then begin by mixing it with two 
or three times its weight of earth, leaving it to dry, and 
afterwards spread it over the soil. We can thus em- 
ploy it direct, but in this case it is important to distin- 
guish that which is assimilable from that which is not. 
Thus apatite can never be turned to account in this 
manner, for, notwithstanding the 80 per 100 of phos- 
phate of lime it contains, its effects will be very 
doubtful. 6 



8u LECTURES ON AGRICULTURE. 

Hitherto the acid phosphate has been employed ex- 
clusively in England. In France, on the contrary, it 
is the direct employment which has prevailed. But I 
have no doubt that our agriculturists will ultimately 
imitate our neighbors in this point, which seems to me 
to be the wiser plan. 

In our practical manure we have included a fourth 
element, potassa: it remains for me to give you its 
history. 

I have previously shown you the necessity for its 
presence in the soil, and the impossibility of substi- 
tuting soda for it, which has now replaced it in most 
manufacturing processes. With manure, substitutions 
are impossible, for each principle has distinct and ex- 
clusive properties. The vegetable is a reagent, which 
distinguishes the slightest shades of difference. You 
will have a fresh proof of this on studying the form 
under which the potassa has most efficacy. Chloride 
of potassium, sulphate of potassa, and the carbonate of 
the same base, are all three soluble in water ; all three 
are absorbed by the roots ; yet the chloride is com- 
pletely inactive, the sulphate produces only an insig- 
nificant effect, and the carbonate gives the best results. 
We also obtain excellent effects with silicate of potassa 
containing sufficient silica to prevent its being attacked 
by water, except very slowly. It is under this form 
that I have always employed potassa in my experi- 
ments on a small scale. This salt possesses the ad- 
vantage of furnishing that alkali, in proportion, so to 
speak, to the wants of the plant. But its employment 
on the large scale is impossible, because its price is 



LECTURES ON AGRICULTURE. 83 

much too high. Besides, it acts only after being con- 
verted into carbonate under the influence of the car- 
bonic acid in the soil. It is, therefore, preferable to 
have direct recourse to carbonate of potassa, which is 
both the most active and the most economical form 
under which this agent can be procured. 

There is, however, another salt, which would be 
much more advantageous if it could be obtained at a 
low price; viz., nitrate of potassa. It contains, at the 
same time, 50 per 100 potassa and 14 per 100 nitro- 
gen, both eminently assimilable; so that, mixed with 
phosphate of lime and lime, it constitutes a complete 
manure. 

Unfortunately, its price is now 51.?. per cwt. If we 
reckon the 15^ lbs. of nitrogen it contains at i$d., 
there still remains nearly 34.?. for the 56 lbs. of potassa, 
which makes 68s. for 112 lbs., while in its other com-, 
pounds it costs only 425-. 6d. per cwt. Still, I have 
thought it my duty to point out to you the advantages 
of nitrate of potassa, which contains upwards of 60 
per 100 of assimilable matter, in order to stimulate 
chemists to seek the means of producing it econom- 
ically. 

The sources of potassa are not very numerous. For 
several years past all that has been found in commerce 
was obtained by washing the ashes of plants. America 
and Russia have for a long time been the principal 
sources of supply; and it was an excellent thing — 
that the wild desert should be impoverished to enrich 
the industry of civilized countries. 

Along with the potashes of Russia and America, 



84 LECTURES ON AGRICULTURE. 

that obtained in the manufacture of sugar from beet- 
root has of late years been placed. This plant, in fact, 
draws from the soil considerable quantities of potassa, 
which is found in the residues of its distillation, or in 
the molasses which remains after the crystallization of 
its sugar. It is only necessary to evaporate the wash, 
and calcine the residue, in order to obtain the car- 
bonate of potassa. 

This manufacture has rapidly taken a great develop- 
ment, and yields large profits to those engaged in it : 
but it ruins the soil in which the beetroot is grown. 

Twenty years ago, the beetroot grown in the neigh- 
borhood of Lille gave a juice very rich in saccharine 
matter; at the present day, notwithstanding. the addi- 
tion of abundance of manure, and the application of 
the most perfect system of cultivation, a juice contain- 
ing more than 5 or 6 per 100 cannot be obtained, con- 
sequently it is only available as food for cattle. The 
reason of this is very plain : the manures employed 
restore to the soil only very small quantities of potassa, 
insufficient to repair the losses caused by the abundant 
exportation just alluded to. 

If the agriculturist desires to restore sugar to his 
beetroot, he must supply the soil with potassa. But 
then he will have to sacrifice the greater part of the 
capital he has derived from the sale of the potassa in 
former years. 

Fortunately new sources of a supply of potassa are 
growing up, and I have every reason to believe that 
agriculture will soon be supplied with it at a low 
pi ice. 



LECTURES ON AGRICULTURE. $5 

I shall first mention the extraction of potassa from 
greasy wool, a branch of industry newly created by 
Messrs. Maumene and Rogele. These gentlemen 
collect the waters of the first washing of the fleece 
before dyeing it, evaporate them in large vats, and 
calcine the residue in gas retorts. They thus obtain a 
very brilliant gas, and as a residue crude carbonate of 
potassa, which is left in the retorts. 

This is a very interesting source, as it returns to the 
service of industry a quantity of potassa which hith- 
erto was absolutely lost. But it is not susceptible of 
a very great extension, and, in fact, it is still from the 
potassa derived from agriculture that the return to the 
soil will serve, in a certain measure, to maintain its 
fertility ; but we cannot, in any way, raise its power 
of production. 

There is still another manufacture which promises, 
at some future day, to reduce the price of the salts of 
potassa. 

Formerly, in the manufacture of sea salt, the mother- 
waters were cast into the sea. 

M. Balard, by patient and laborious studies, has suc- 
ceeded in showing that these mother-waters may be 
made to yield several useful salts at little expense. 

M. Balard's processes, modified by M. Merle, who 
is established at Camargue, operate on a very large 
scale, and produce considerable quantities of chloride 
of potassium. 

Sea water is submitted to a first evaporation in the 
sun, in consequence of which it deposits four-fifths of 
its chloride of sodium. The mother-waters are then 



86 LECTURES ON AGRICULTURE. 

removed to special reservoirs, where they are suddenly 
cooled to 32 degrees below freezing point by M. Carre's 
ice-making machine. At this low temperature double 
decomposition takes place between the remaining 
chloride of sodium and the sulphate of magnesia, from 
which results sulphate of soda, which crystallizes, and 
chloride of magnesium, which remains in solution. 
After the removal of the sulphate of soda the mother- 
water contains only chloride of magnesium and chlo- 
ride of potassium, which are made to deposit by a fresh 
refrigeration in appropriate vessels. A washing after- 
wards removes the chloride of magnesium, and leaves 
the much less soluble chloride of potassium almost in 
a state of purity. 

I have visited M. Merle's establishment, and I can 
assure you that it is an exciting spectacle to see these 
immense refrigerators working with the regularity of 
steam-engines, and continuously converting the moth- 
er-waters in basins of several acres of surface into a 
snow of sulphate of soda on the one hand and chloride 
of potassium on the other. Here is an unlimited 
source of this salt which will render the greatest ser- 
vices to agriculture, when its conversion into carbonate 
shall be arrived at, for, as I have before stated, it 
cannot be employed in its natural state. 

I was enthusiastic with this magnificent manufac- 
ture, but I have recently learned of the existence of 
another, which appears to me to be still more im- 
portant. 

Felspathic rocks, which in many countries exist in 
inexhaustible masses, all contain potassa. Orthose 



LECTURES ON AGRICULTURE. 87 

contains as much as 14 per 100. This potassa, en- 
gaged in insoluble combinations, is completely inert ; 
it becomes accessible to vegetation only after the dis- 
aggregation and decomposition of the rocks of which 
it forms a part. Now these rocks decompose only 
with extreme slowness under the influence of atmos- 
pheric agents ; and to estimate the effect of this decom- 
position, we must reckon time by geological periods. 

To separate, by rapid and economical means, the 
potassa contained in feldspars, has for a long time 
been one of the most exciting problems of manufac- 
turing chemistry. Many solutions have been pro- 
posed, but none of them have been successful in 
furnishing potassa really cheap. Messrs. Ward and 
Wynants, of Brussels, have solved this difficulty. 
They attack the feldspars by treating them with car- 
bonate of lime and fluoride of calcium. The mass is 
next treated with water, which extracts the whole of 
the potassa in the state of carbonate. This reaction 
demands only a moderate temperature, and leaves a 
useful residue ; it is therefore in excellent practical 
condition. The inventors are striving to perfect the 
manufacture, and as the success of their enterprise will 
be a great boon to agriculture, we will conclude, gen- 
tlemen, by wishing them success. 



LECTURE SIXTH. 



ANALYSIS. 

Summary of the Foregoing Propositions. — Comparison of 
the New System with past Traditions and Practice. — The 
Dunghill the Manure /ar excellence. — Analysis of its 
Chemical Constituents proves that it contains the four es- 
sential fertilizing Agents : Phosphoric Acid, Lime, Potassa, 
and Nitrogenous Matter. — An exact Balance with regard 
to these four Agents exists among all the Systems of' 
Cultivation, z. e., between the Quantities supplied by the 
Manure and that carried away in the Crops. — Results of 
the Triennial Rotation of Crops. — Results of the Five 
Years' System. — Mean Annual Return of the two Systems. 

— Results of various Cultivations. — Beetroot. — Colza. 

— Advantages of the New System; maintains the Fertility 
of the Soil unimpaired, whatever Crops are continuously 
grown, without Rotation. — Comparison of the Quantities 
of the four fertilizing Agents contained in various Crops 
and in the Complete Manure. — Power of Production of the 
Old Processes of Cultivation, compared with those of the 
New System. — Law which regulates the New System, 
which throws down the Barriers that have hitherto limited 
Production. — Estimate of the Results of its Adoption in 

SS 



LECTURES ON AGRICULTURE. 89 

France. — Conclusion. — Results of the Harvest of 1864 
on the New System. 



ALL that I have stated to you previously may be 
summed up in the two following propositions : 

1st. — There exist four regulating agents par ex- 
cellence in the production of vegetables : nitro- 
genous matter, phosphate of lime, potassa, and 
lime. 

2d. — To preserve to the earth its fertility, we 
must supply it periodically with these four sub- 
stances in quantities equal to those removed by 
the crops. 

Such, in their greatest simplicity, are the conclu- 
sions to which we have been unavoidably led by the 
discussion of the scientific experiments upon vegeta- 
tion. Let us now examine to what point these results 
agree with the results of practice, and the traditions of 
the past. 

It is an admitted law in agriculture, that the soil 
will not yield crops without manure, and the manure 
par excellence which practice has realized, is the farm 
dunghill : a collection of all the residues of the har- 
vest, a true caput mortuum of agricultural opera- 
tions. 

I do not know what the composition of the dunghill 
is, although I do not hesitate to assert that it includes 
the four agents of vegetable production : for, without 
their presence, its good effect would be incomprehen- 
sible. Here is its analysis. 



9 o 



LECTURES ON AGRICULTURE. 



COMPOSITION OF THE DRY MANURE. 

Imperial Farm Farm at 

at Vincennes. Bochelbronn. 



Organic 

Elements. 



Mineral 
Elements 



(Carbon 
Hydrogen 1 59.65 
Oxygen J 
Nitrogen 2.08 

' Phosphoric Acid 0.88 

Sulphuric Acid traces 

Carbonic Acid 0.94 

Chlorine 0.70 

Ammonia and Oxide of Iron 0.68 

Lime 5.23 

Magnesia 0.32 

Potassa 2.46^ 

Soda traces; 

Soluble Silica ...... 1.41 

Sand 25.66 



35-5 

4.2 

25.8 



100-09 
(G.Ville. 



65-5o 

2.00 
1. 00 

0.65 
0.66 
0.20 
2.03 
2.81 
1.20 

2.60 
22.13 



100.78 



(Bous- 
singault.) 



Thus we find in the manure, the use of which is 
consecrated by time, phosphoric acid, lime, potassa, 
and nitrogenous matter, the same substances which 
our researches have pointed out to us as being the 
starting-point of all production. 

Assuredly this coincidence is not the effect of chance. 
Our first proposition is then found to be fully verified. 
Let us see if it is the same with the second. To that 
end it will suffice to pass in review the system of cul- 
tivation most generally pursued, and to show that an 
exact balance, with regard to the four agents, exists 
among them all, between the quantity brought by ma- 
nure, and that carried off by the crops. Upon this 



LECTURES ON AGRICULTURE. 



9 1 



second point the demonstration will be as conclusive 
as upon the first. 

The most ancient system of cultivation, which neces- 
sity devised, and practice recognized for maintaining 
the fertility of the soil, is that which is still employed 
in many countries under the name of Triennial Rota- 
tion. Every three years the soil receives eight tons of 
manure per acre ; it lies one year in fallow, and after- 
wards produces two crops of wheat. 

The results of this system are given on page 92. 

You see that the balance is strikingly exact with 
regard to the nitrogen and the phosphoric acid ; as to 
the potassa and lime, it accumulates for the benefit of 
the soil. 

There is, then, nothing surprising in the fact of this 
system maintaining the fertility of the soil, as nothing 
is lost; but upon what conditions? 

To obtain these eight tons of manure required every 
three years, we must raise cattle ; to feed them re- 
quires pasture ; and to maintain this pasture requires 
irrigation. It is then, in fact, from the water of irriga- 
tions that the triennial rotation derives the four agents 
which it exports under the form of grain, and to obtain 
them it is obliged to devote one-third of the farm to 
pasture. Fallow and pasture, then, are the plagues of 
the triennial system. 

Agriculture has for a long time endeavored to es- 
cape from fallowing. It has succeeded by introducing 
clover and similar plants into the rotation. In this 
manner the rotation is extended to five years. The 
crops of clover and roots have nourished the cattle, 



92 



LECTURES ON AGRICULTURE. 



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93 



and the system has sufficed for itself. Here, also, are 
the data to which it gives rise. (See table, page 94.) 

The triennial system accumulates important quanti- 
ties of alkalies and lime in the soil as pure loss. But 
through the clover and the roots, which have a marked 
preference for these elements, they are in great meas- 
ure turned to account. But the greatest advantage of 
the five-year rotation consists in its influence with re- 
gard to nitrogen. You see that the cost of this ele- 
ment was repaid in benefiting the crops, and if you 
seek the plant to which this benefit is due, you will 
find that it is the clover, to the vegetable that forms 
part of the system. 

You will remember that, while the cereals draw the 
greater part of their nitrogen from the soil, vegetables, 
on the contrary, obtain it from the atmosphere. Thus 
you perceive, that the crop of wheat which follows the 
clover is more abundant, and contains more nitrogen, 
than that which preceded it — which proves that the 
clover has not impoverished the soil of that element. 

The five-years' rotation, therefore, realizes the con- 
tinuous culture. It has two important advantages 
over the preceding. 1. It derives a portion of the ni- 
trogen of the crops from the atmosphere. 2. It turns 
to account the excess of potassa and lime brought by 
the manure. And the crops are also more abundant, 
as is shown by the following table. 

MEAN ANNUAL RETURN OF THE TWO SYSTEMS. 

Triennial. Quinquennial. 

Weight of dried crop, per acre 2455 lbs. 3131 lbs. 

Nitrogen contained in this crop 25 lbs. 44 lbs. 

With the five years' rotation, agriculture has been 



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LECTURES ON AGRICULTURE. 95 

brought to substitute the exportation of meat for that 
of the cereals, and it has derived decided advantages 
from the substitution ; for the sale of the cereals causes 
a loss of potassa, phosphoric acid, and nitrogen to the 
farms, which cannot be compensated for except by a 
supply of manure, or by irrigation. If, on the contra- 
ry, the crops are consumed on the farm by the ani- 
mals, we find in their excrements almost the whole 
of the phosphoric acid and potash contained in their 
food. The quantities that fix themselves in their tis- 
sues and bony structure, constitute but a small loss. 
As to the nitrogen, their respiration rejects about a 
third of it into the atmosphere, in the gaseous state ; 
the other two-thirds return to the soil in the manure. 
This would be a loss, inevitably impoverishing the 
farm, without the clover, which derives an equivalent 
quantity from the atmosphere. 

It follows, from this, that the raising of cattle results 
in preserving to the soil almost the whole of the four 
agents which assures its fertility, and of procuring 
benefits in money without sensibly impoverishing the 
farm. 

You see that the five years' system no more opposes 
our conclusions than the triennial ; they receive, on 
the contrary, an unexpected light, and consequently 
afford them a striking confirmation. 

But,. you will ask, is this the best practice devised? 
No, gentlemen. There exists a cultivation which real- 
izes considerable profits, and which, when well carried 
out, causes almost no loss at all to the soil — * that is 
the manufacturing cultivation of beetroot. In this 



96 LECTURES ON AGRICULTURE. 

case the exports are sugar or alcohol, substances ex- 
clusively composed of carbon, oxygen, and hydrogen, 
derived from water and the atmosphere. The ex* 
pressed pulp serves to nourish the cattle, and almost 
the whole of the useful elements are returned to the 
soil, especially if care be taken to mix the residue of 
distillation with the manure, instead of extracting the 
potash. 

Such are the systems of agriculture, developed dur- 
ing ages of groupings, true arc of promise to agricul- 
ture, in which it had been rash to make the least 
attack. Now we see them brought to rational and 
positive notions, and science, which has learned to un- 
veil the mysteries of their success, will learn also to 
give them the last improvement of which they are sus- 
ceptible. Without quitting the ways of the past, it 
will point out a simpler and more perfect method, 
which will be the ideal realization of the principle to 
which practical agriculture has always instinctively en- 
deavored to conform itself, and constantly approached, 
and which we can now formularize in few words. 

Cultivate the soil, and realize its profits, without 
impoverishing it of the four agents which assure its 
fertility. 

In all the systems I have described, and even in the 
case of beetroot, the farm always loses the nitrogen 
which the animal dissipates in the elementary state, 
and the universal salts contained in the cattle exported. 

A system, from which these losses were banished, 
would be the crown of the old method. It is colza 
that furnishes it. 



LECTURES ON AGRICULTURE. 97 

Its seed contains oil, a product of great value, and, 
like sugar^ composed of carbon, oxygen, and hydrogen. 
Imagine an estate exclusively devoted to the cultiva- 
tion of colza, and that an oil-mill is attached to it. 
The oil will be exported, and will yield returns in 
cash ; all the rest, stems and oil-cake, will be returned 
to the soil without even passing through the medium 
of cattle. To this end we must add to the extraction 
of oil by pressure, a supplementary extraction by so- 
lution. The oil-cake, upon being removed from the 
hydraulic press, still contains 14 per 100 of oil, and 
sells at 6s. 6d. the cwt. The oil alone which they 
contain possesses this value. The substance of the 
oil-cake is thus gratuitously lost to the farm. When 
the oil is extracted by an appropriate solvent, sulphide 
of carbon, for example, in closed apparatus, constructed 
in such a manner that a small quantity of this liquid 
put in circulation may exhaust considerable masses of 
it, there will remain a dry and pulverulent oil-cake? 
containing all the products extracted from the soil. 
They are mixed with the stems on the dungheap, and 
water is added. Putrefaction soon sets in, and we ob- 
tain an excellent manure, which restores to the soil 
the whole of the elements which the crops had re- 
moved from it, and which received the benefit of all 
the nitrogen derived from the atmosphere. 

After having discovered by what series of compen- 
sations the practice of the past arrived at conforming 
to the superior laws of vegetable production — laws of 
which it knew nothing — science may even imagine a 
simpler system, from which animals, and the loss they 

7 



98 LECTURES ON AGRICULTURE. 

cause, are excluded, and which, yielding important 
profits, while enriching the soil, presents itself as the 
last degree of perfection to which it is possible to 
arrive by the methods of the past. 

But the fertility of the principles I have explained 
do not stop there. We must now abolish the practices 
pointed out to you, and replace them by a simpler agri- 
culture, more mistress of itself, and more remunera- 
tive. Instead of compelling ourselves by infinite cares 
and precautions to maintain the fertility of the soil, we 
reconstitute it, in every respect, by means of the four 
agents which I have pointed out, and which we can 
derive from the great stores of nature. Then no rota- 
tion of crops is necessary, no cattle, no particular choice 
in cultivation. We produce at will, sugar or oil, meat 
or bread, according as it best serves our interest. We 
export without the least fear the whole of the products 
of our fields, if we see our advantage in so doing. 
We cultivate the same plant upon the same soil, in- 
definitely, if we find a good market for the produce. 
In a word, the soil is to us in future merely a medium 
of production, in which we convert at pleasure the four 
agents in the formation of vegetables into this or that 
crop which it suits us to produce. We are restrained 
only by a single necessity : to maintain at the disposal 
of our crops these four elements in sufficient propor- 
tion, so that they may always obtain the quantity their 
organization demands. 

Let us see to what point this condition is fulfilled 
in our new methods. To this end, it will be sufficient 
to compare the composition of the crops obtained from 



LECTURES ON AGRICULTURE. 



99 



the farm at Vincennes with that of a complete ma- 
nure. 

QUANTITIES OF THE FOUR AGENTS CONTAINED 
" IN THE CROPS AND IN THE COMPLETE MA- 
NURE — PER ACRE. 



Crops. 
In the Year 1861. 


Weight of 

the Crops, 

dried. 


Nitrogen. 


Phosphoric 

Acid. 


Potassa. 


Lime. 




Lbs. 


Lbs. 


Lbs. 


Lbs. 


Lbs. 


Spring Wheat 


6.080 


73-030 


26.36 


38.02 


17.80 


Beet Root. . . 


8.972 


289.530 


46-59 


134.21 


67.56 


Barley .... 


7.058 


108.89 


33-22 


72.06 


35-86 


Peas 


5- H5 


148.17 


35-6o 


82.39 


112.93 






i53-io 

In the state 
of Nitrate 
of Soda, or 

of Sal 
Ammoniac. 


176.00 

In the»state 

of 
Phosphate 
of Lime. 


176.00 

In Vhe state 

of 
Carbonate 

of 
Potassa. 


176.00 

In the state 

of 

Caustic 

Lime. 


1 


! 



You perceive, gentlemen, that our new system satis- 
fies the law of equilibrium as well as the systems of 
the past : only, we hold the balance in our hands, and 
in proportion as one of the scales tends to rise, we 
restore the equilibrium by loading the other with an 
equal weight. 

In the old systems, in which we maintained the 
equilibrium blindly, it frequently happened that one 
of the useful elements partially failed, and that the 
crops were also deficient. With the new processes, 
the plants finding in abundance all they require, al- 
ways attain their maximum of possible development ; 



100 LECTURES ON AGRICULTURE. 

the crops are also much more abundant, as may be 
seen by the following table. 

POWER OF THE PRODUCTION OF THE OLD PRO- 
CESSES OF CULTIVATION, COMPARED WITH 
THOSE OF THE NEW SYSTEM. 

Yield per Acre. 



Old Processes. New Processes. 

C Straw 8.250 } Straw . . 
Wheat < V11.S89 ^23.520 

£ Grain 3.639 ) Grain . . 




C Straw 5.414} Straw . . 

Peas < > 7.610 ^ 12.863 

(Grain 2.196) Grain . . 

Beetroot Roots • . . .6.978 Roots 20.110 

But it is not sufficient to indicate the means of pro- 
ducing abundant crops ; we must also show the method 
to be followed in order to obtain them economically. 

The application of complete manures creates fertil- 
ity everywhere ; but it is not everywhere nor always 
necessary to have recourse to so expensive a com- 
pound. 

When we suppress any of the constituent agents — 
the nitrogenous matters, for example — the yield of 
wheat immediately undergoes a considerable reduc- 
tion, but that of peas and vegetables is not affected by 
it. Suppress, on the contrary, the potassa : then the 
yield of the vegetables suffers most. For turnips, 
parsnips, and roots generally, it is the suppression of 
phosphate of lime which produces the worst effects. 
These results lead us to admit that among the four 
agents in each kind of crop there is one which exer- 
cises a more particular influence upon the yield. 



LECTURES ON AGRICULTURE. IOI 

We, therefore, formularize the following law, which 
will regulate the new agricultural practice. 

Although the presence of the four agents of fertility 
in the soil is necessary and indispensable for all plants, 
the exigences of various cultivations are not the same 
with regard to the quantities of each of these agents — 
or, in other words, each crop has its leading one. 

Thus, nitrogenous matter is the dominant agent for 
wheat and beetroots, potash for vegetables, phosphate 
of lime for roots, &c. 

Suppose we undertake the cultivation of a piece of 
poor land. We begin by giving it the complete ma- 
nure, in order to create a sufficient provision of the 
four agents of fertility. We raise one or two crops of 
cereals upon this manure ; then we continue the cul- 
ture by giving to the soil, each year, the dominant 
element of the crop we propose to raise. 

If we adopt a rotation of four years with such crops 
that, at the end, has received the four agents, we can 
continue thus indefinitely without ever requiring the 
complete manure. The same system is applicable to 
a fertile soil ; only we may dispense with the first dose 
of complete manure, and commence immediately by 
the dominant element of the first crop we desire to 
raise. 

If, on the contrary, it be desired to continue the 
same crop indefinitely, we content ourselves generally 
with the employment of its dominant ; but taking care 
to resume the application of the complete manure, 
immediately that a slight reduction in the weight of 
the crop points out the necessity for so doing. 



102 LECTURES ON AGRICULTURE. 

By these simple combinations we are in possession 
of a new agriculture, immeasurably more powerful 
than its predecessor. 

Formerly, the total matter placed by nature at the 
disposal of organized beings like ourselves, had its 
limits. All that the systems in vogue could do, was 
to maintain it ; but none succeeded in increasing it. 

With regard to the problems of life and population, 
human power encounters an impassable limit. The 
new processes of cultivation will have the effect of 
suppressing this barrier. Under their influences mat- 
ters at present without value, which scarcely serve as 
materials of construction, and of which nature pos- 
sesses inexhaustible stores, can be converted into vege- 
table products : — forage to nourish the animals upon 
which we feed ; and cereals, to produce bread, the 
most valuable of our resources. From this the great 
stream of organized matter which sustains every exist- 
ence will be increased with new waves, and the level 
of life will continue unceasingly to rise to the surface 
of the globe. 

But, gentlemen, beneath these great results which 
present themselves to the philosophic mind, there are 
others, more immediate, more practical, — if I may so 
express myself, — which the system I strive to make 
prevail also carries on its flanks. 

Since the Revolution of 1789, the territory of France 
has continually been parcelled out in smaller portions. 
This fact has often been proclaimed ; but the evil still 
continues unremedied. 

According to official returns, the superficial area of 
France is now divided as follows : 



LECTURES ON AGRICULTURE. 



103 



Nature of the Property. 


Mean 
Extent. 


Surface 
occupied. 


Corresponding 
Population. 


Large Estates 

Medium Estates .... 

Small Estates 

Very small Estates . . . 


Acres. 
415 
87.50 

35 
8.62 


Acres. 
43,320,000 
19,250,000 
16,800,000 
36,130,000 


1,000,000 

1,000,000 

2,400,000 

19,500,000 


Totals 




115,500,000 


24,000,000 



Of the one hundred and fifteen millions of acres of 
cultivated land, there are thirty-six millions possessed 
by proprietors whose estates do not exceed eight and a 
half acres in extent. What kind of agricultural sys- 
tem can a man pursue who possesses only eight acres 
for everything, and who requires as much for the sup- 
port of his family? How, and with what, will he 
obtain manure? He can have neither meadows nor 
cattle. He must necessarily farm badly ; his land is 
fatally condemned to sterility, and himself to poverty. 

To combine the agents of fertility which have re- 
posed in geological strata since the foundations of the 
earth were laid, to place them at the disposal of the 
small farmer, will be to give fertility to fifty millions 
of acres devoted to the small and minimum cultivation, 
and create prosperity among twenty out of the twenty- 
four millions occupied in agricultural industry. 

Now I ask you, gentlemen, if these views are not 
superior to the finest dreams of charity and philan- 



104 LECTURES ON AGRICULTURE. 

thropy? Would they not also, if they were merely in 
the condition of scientific conceptions, suffice to excite 
our zeal? But experience has returned its verdict. 
The crops you have before your eyes prove that with 
a manure, averaging in cost about five pounds a year, it 
is possible to obtain abundant harvests. Reduce, if 
you will, the excess of production, per acre, to a ton, 
which is here raised above three tons ; and applying 
this data to the fifty millions of badly cultivated acres, 
and see to what financial results we shall be inevita- 
bly led. 

The first movement in this direction will create a 
demand for fertilizing materials to the extent of some 
millions. What an impulse this must give to com- 
merce ! 

Next, to obtain twenty millions of tons more wheat 
than French agriculture supplies at the present time, 
and consequently an increase of wealth of about five 
millions sterling. What a guaranty against famine ! 

What is required to accomplish such a revolution? 
We must apply the principles I have explained to you, 
and generalize them. In the second place, commerce 
must place the agents of fertility under the protection 
of 'new institutions of credit. They must be so con- 
ceived that the advances for the necessary manures may 
be made to the small farmer, to be repaid out of the 
excess of crops derived from the fertilizers. 

The solution of this problem connects itself in a sin- 
gular manner with social and political destinies. Every- 
where the approach of democracy manifests itself. Is 
this a good? Is it an evil? I am not competent to de- 



LECTURES ON AGRICULTURE. 105 

cide the question : but it is very certain that at the 
present time the greater part of agricultural population 
deserts the country to seek an easier condition of life 
in the cities. 

This immense class, second only to the working 
population of the cities, represents, in a high degree, 
the true public spirit. 

To change its economic situation, to put it into a 
condition of more intensive cultivation, notwithstand- 
ing the exigences of the scale upon which it operates, 
is to attach it to the soil by its own interests. By this 
means a large conservative party may be created, with- 
out which a democracy based upon commerce will 
grow up, leading only to a crisis analogous to that 
which now presents so deplorable a spectacle in 
America. 

England has avoided this danger at the price of an 
enlightened and patriotic aristocracy, but whose exist- 
ence perpetuates an inequality in human destinies 
which conscience repudiates and the laws of humanity 
condemn. Neither England nor America, therefore, 
have solved the problem of a powerful, wise, and just 
democracy. 

To me, it seems that our beautiful country is pre- 
destined to give this great example to the rest of the 
world, and I have the firm hope that the principles I 
have placed before you, in the course of these lectures, 
will serve as the starting-point to the realization of this 
inestimable result. 



APPENDIX, 



EXPERIMENTAL FARM AT VINCENNES. 
Harvest of 1864. 

On the 31st of July, M. George Ville reaped and threshed 
his crops in presence of a large concourse of agriculturists. 
The results were as follows : — 

WHEAT. 

Third Crop from the same land without fresh manure since 

the first application. 
Crop per Acre. Without Manure. With Complete Manure. 

Straw 704 lbs 5>9i3 lbs. 

Grain 193 lbs 2,464 lbs. 

Total .... 0,897 lbs 8,377 lbs - 

Fourth Crop without fresh manure since the first. 
Crop per Acre. Without Manure. With Complete Manure. 

Straw 1,074 lbs 4,629 lbs. 

Grain 316 lbs 1,760 lbs. 



Total .... 1,390 lbs 6,389 lbs. 

COLZA. 

Coming after txuo crops of Barley without fresh manure. 
Crop per Acre. Without Manure. With Complete Manure. 

Straw and Silicates 5,632 lbs 7>7oo lbs. 

Grain 1,320 lbs 2,410 lbs. 



Total .... 6,952 lbs 10,110 lbs. 

106 



APPENDIX. I07 

Crops of 1864. 

BEETROOT. 

On the 30th of October the crop of Beetroots was publicly 
got in. The results obtained were as follows : — 

1. Soil without Manure. 

Crop per Acre. 
Leaves 6,204 lbs- 
Roots 16,544 lbs - 

Total 22.748 lbs. 

This piece of land, put under cultivation in 1861, had pre- 
viously yielded two crops. 

In 1861. In 1862. 

Crop per Acre. 

Leaves .... 14.696 lbs. Leaves .... 7,040 lbs. 

Roots .... 44,616 lbs. Roots 12,056 lbs. 

59,312 lbs. 19,096 lbs. 

In 1863 the crops were devoured by the white worm, con- 
sequently there was no return, and this year's crop was a 
little increased by the preceding year being fallow. 

2. Soil with Complete Manure. 

Crop per Acre. 

Leaves 6.618 lbs. 

Roots 24.990 lbs. 

31,608 lbs. 

This piece of land, like the preceding, had furnished two 
previous crops since it received any manure. 

In 1861. In 1862. 

Crop per Acre. 

Leaves .... 14,344 1ds « Leaves .... 9,680 lbs. 

Roots .... 47,960 lbs. Roots .... 21,820 lbs. 

62,304 lbs. 31,500 lbs. 



I08 LECTURES ON AGRICULTURE. 



But which has received acid phosphate of lime instead of 
ordinary phosphate. 

Leaves • 7,700 lbs. 

Roots 30,624 lbs. 

38,324 lbs. 
This piece of land had also yielded two crops previous, 
since it had received any manure. 

In 1861. In 1862. 

Crop per Acre. 

Leaves . . . . 15,488 lbs. Leaves . . . .11,000 lbs. 

Roots .... 78,7S6 lbs. Roots .... 33,968 lbs. 



94,274 lbs. 44,968 lbs. 

4. Land with Complete Manure. 

Crop of Beetroot coming after three fine crops of Wheat 
without fresh manure. 

Crop per Acre. 

Leaves 7,304 lbs. 

Roots 36,826 lbs. 



44,130 lbs. 



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